Benzimidazolo[1,2-a]benzimidazole carrying aryl- or heteroarylnitril groups for organic light emitting diodes

ABSTRACT

Novel benzimidazolo[1,2-a]benzimidazoles carrying aryl- or heteroarylnitril groups, an electronic device, comprising said novel benzimidazolo[1,2-a]benzimidazoles carrying aryl- or het-eroarylnitril groups, which is preferably an electroluminescent device, a charge transport layer, a charge/exciton blocker layer, or an emitting layer comprising said novel benzimidazolo[1,2-a]benzimidazoles carrying aryl- or heteroarylnitril groups, an apparatus selected from the group consisting of stationary visual display units; mobile visual display units; illumination units; key-boards; items of clothing; furniture; wallpaper, comprising said organic electronic device, or said charge transport layer, said charge/exciton blocker layer, or said emitting layer.

The present invention relates to compounds of formula I and their use inelectronic devices, especially electroluminescent devices. When used ascharge transport material, charge blocker material and/or host materialin electroluminescent devices, the compounds of formula I may provideimproved efficiency, stability, manufacturability, or spectralcharacteristics of electroluminescent devices and reduced drivingvoltage of electroluminescent devices. Also, said compounds of formula Ishow low singlet triplet splitting, which makes them useful as TADF(Thermally Activated Delayed Fluorescence, Adv. Mater. 2014, 26,7931-7958) emitter or TADF host materials in combination withfluorescent emitters.

Khan, Misbahul Ain; Ribeiro, Vera Lucia Teixeira, Pakistan Journal ofScientific and Industrial Research 43 (2000) 168-170 describes thesynthesis of benzimidazo[1,2-a]benzimadozoles

(R=H, Me, Et) by trialkyl phosphite-induced deoxygenation andthermolysis of 1-(o-nitrophenyl)- and 1-(o-azidophenyl)benzimidazoles.

Pedro Molina et al. Tetrahedron (1994) 10029-10036 reports that azaWittig-type reaction of bis(iminophosphoranes), derived frombis(2-aminophenyl)amine with two equivalents of isocyanate directlyprovided benzimidazo[1,2,a]benzimidazole derivatives.

R=iso-propyl and R′=ethyl)

Kolesnikova, I. V.; Zhurnal Organicheskoi Khimii 25 (1989) 1689-95describes the synthesis of 5H-benzimidazo[1,2-a]benzimidazole1,2,3,4,7,8,9,10-octafluoro-5-(2,3,4,5,6-pentafluorophenyl).

Achour, Reddouane; Zniber, Rachid, Bulletin des Societes ChimiquesBelges 96 (1987) 787-92 describes the synthesis ofbenzimidazobenzimidazoles

(R=H, —CH(CH₃)₂) which were prepared from benzimidazolinone derivatives.

Hubert, Andre J.; Reimlinger, Hans, Chemische Berichte 103 (1970)2828-35 describes the synthesis of benzimidazobenzimidazoles

X. Wang et al. Org. Lett. 2012, 14, 452-455 discloses a highly efficientcopper-catalyzed synthesis for compounds of formula

wherein compounds of formula

are reacted in the presence of copper acetate(Cu(OAc)₂)/PPh₃/1,10-phenanthroline/sodium acetate and oxygen inm-xylene (1 atm) at elevated temperature. Among others the followingcompounds can be prepared by the described synthesis method:

In Eur. J. Org. Chem. 2014, 5986-5997 a new synthesis ofbenzimidazolo[1,2-a]benzimidazole is described.

In RSC Advances 2014, 4, 21904-21908 a new synthesis ofbenzimidazolo[1,2-a]benzimidazole is described.

It is mentioned—as a general statement—that these polycyclic moleculeshave—besides other applications—also attracted great interest in thefield of electroluminescent devices.

WO2011/160757 relates to an electronic device comprising an anode,cathode and at least one organic layer which contains a compound offormulae

wherein X may be a single bond and L may be a divalent group. Thefollowing 4H-Imidazo[1,2-a]imidazole compounds are explicitly disclosed:

WO2012/130709 relates to 4H-Imidazo[1,2-a]imidazoles,

such as, for example,

a process for their production and their use in electronic devices,especially electroluminescent devices.

WO2013/068376 describes 4H-imidazo[1,2-a]imidazoles of formula

wherein X⁶ is —N═ and X⁷ is —NR⁶—, or X⁷ is ═N— and X⁶ is —NR⁶—, R⁶ is agroup of formula

such as, for example,

a process for their production and their use in electronic devices,especially electroluminescent devices.

WO2014/009317 relates to compounds of formula

especially compounds of formula

such as, for example,

a process for their production and their use in electronic devices,especially electroluminescent devices. The 2,5-disubstitutedbenzimidazo[1,2-a]benzimidazole derivatives are suitable holetransporting materials, or host materials for phosphorescent emitters.

WO2014/044722 relates to compounds of formula

which are characterized in that they substituted bybenzimidazo[1,2-a]benzimidazo-5-yl and/orbenzimidazo[1,2-a]benzimidazo-2,5-ylene groups and in that at least oneof the substituents B¹, B², B³, B⁴, B⁵, B⁶, B⁷ and B⁸ represents N, aprocess for their production and their use in electronic devices,especially electroluminescent devices.

European patent application no. 13191100.0 relates to compounds offormula

which are characterized in that they are substituted bybenzimidazo[1,2-a]benzimidazo-5-yl and/orbenzimidazo[1,2-a]benzimidazo-2,5-ylene groups and in that at least oneof the substituents B¹, B², B³, B⁴, B⁵, B⁶, B⁷ and B⁸ represents N; aprocess for their production and their use in electronic devices,especially electroluminescent devices.

European patent application no. 14162667.1 relates to compounds of theformula

especially

wherein X¹ is H, a group of formula

X² and X³ are independently of each other H, or a group of formula

wherein at least one of X¹, X² and X³ is a group of formula

or comprises a group of formula

Benzimidazo[1,2-a]benzimidazo-5-yl andbenzimidazo[1,2-a]benzimidazo-2-yl substitutedbenzimidazolo[2,1-b][1,3]benzothiazole derivatives are described inPCT/EP2014/066174. Azabenzimidazo[2,1-a]benzimidazoles for electronicapplications are described in European patent application no.14183598.3.

European patent application no. EP14197947.9 describes carbazolcompounds carrying benzimidazolo[1,2-a]benzimidazole groups of thefollowing structure.

wherein

m is 1, or 2, n is 0, 1, or 2,

Ar¹ and Ar² are independently of each other a C₆-C₂₄aryl group, whichcan optionally be substituted by G, a C₁₂-C₃₀heteroaryl group, which canoptionally be substituted by G,

A¹ is a group of formula

European patent application no. EP14193401.8 describes nitril-indolocompounds carrying benzimidazolo[1,2-a]benzimidazole groups. Thefollowing compound is described:

European patent application no. EP14197952.6 describes dibenzofuranecompounds carrying benzimidazolo[1,2-a]benzimidazole groups of thefollowing structure.

wherein

-   -   X is O or S;    -   Y is a group of formula —[Ar¹]_(a)—[Ar²]_(b)—[Ar³]_(c)-A¹;

A¹ is a group of formula

The following group is described.

WO2013/154064 A1 discloses an organic light emitting element, which hasa compound of the following formula in the light emitting layer:

wherein at least one of R¹ to R⁵ represents a cyano group, at least oneof R¹ to R⁵ represents a 9-carbazolyl group, a1,2,3,4-tetrahydro-9-carbazolyl group, a 1-indolyl group or adiarylamino group, and the rest of R¹ to R⁵ represent a hydrogen atom ora substituent.

EP 2 039 737 A2 concerns an organic electroluminescence devicecomprising a compound of formula (I)

wherein a represents an aromatic ring which may have a substituent, mrepresents an integer of 2 or greater, and n represents an integer of 1or greater.

Neither WO2013/154064 A1 nor EP 2 039 737 A2 disclose compoundscomprising benzimidazolo[1,2-a]benzimidazole groups.

Notwithstanding these developments, there remains a need for organiclight emitting devices comprising new materials, especially host(=matrix) materials, charge transport materials and/or charge/excitonblocker materials to provide improved efficiency, stability,manufacturability, driving voltage and/or spectral characteristics ofelectroluminescent devices. Further, there is a need for materialsshowing low singlet triplet splitting, which makes them useful as TADF(Thermally Activated Delayed Fluorescence, Adv. Mater. 2014, 26,7931-7958) emitter or TADF host materials in combination withfluorescent emitters.

Accordingly, it is an object of the present invention, with respect tothe aforementioned prior art, to provide further materials suitable foruse in OLEDs and further applications in organic electronics. Moreparticularly, it should be possible to provide charge transportmaterials, charge/exciton blocker materials and host (=matrix) materialsfor use in OLEDs. The materials should be suitable especially for OLEDswhich comprise at least one emitter, which is preferably aphosphorescence emitter, especially at least one green emitter or atleast one blue emitter. It should further be possible to providematerials showing low singlet triplet splitting, which makes them usefulas TADF (Thermally Activated Delayed Fluorescence, Adv. Mater. 2014, 26,7931-7958) emitter or TADF host materials in combination withfluorescent emitters.

Furthermore, the materials should be suitable for providing OLEDs whichensure good efficiencies, good operative lifetimes and a high stabilityto thermal stress, and a low use and operating voltage of the OLEDs.

Said object is solved by compounds of formula (I),

wherein

X³ is a single bond or linking group of formula-(A¹)_(o′)-(A²)_(p′)-(A³)_(q′)-(A⁴)_(r′-),

A¹, A², A³, A⁴ are in each occurrence independently of each other C₆-C₂₄arylene group which is unsubstituted or substituted by at least onegroup G, C₂-C₃₀ heteroarylene group which is unsubstituted orsubstituted by at least one group G, and

o′ is 0 or 1, p′ is 0 or 1, q′ is 0 or 1, r′ is 0 or 1, preferably o′ is0 or 1 and p′ is 0 or 1, and q′ and r′ are 0,

X⁴ is a single bond or

preferably

preferably,

preferably, X⁴ is a single bond or

preferably,

X² is O, S or NR⁶⁵, preferably X² is O, S, more preferably X² is O;

X⁵ is O, S or NR⁶⁵, preferably X⁵ is O, S, more preferably X⁵ is O;

a is 0, 1, 2, 3 or 4,

b is 0, 1, 2, 3 or 4,

preferably, the sum of a+b is 1, 2 or 3, more preferably, 1 or 2, i.e.more preferably, a is 1 or 2 and b is 0, a is 1 and b is 1, or a is 0and b is 1 or 2,

a′ and a″ are independently of each other 0, 1, 2 or 3,

b′ and b″ are independently of each other 0, 1, 2 or 3,

preferably, the sum of a″+b″ is 0, 1 or 2, more preferably 0 or 1;

preferably, the sum of a′+b′ is 0, 1 or 2, more preferably 0 or 1;

X¹, X^(1′) and X^(1″) are independently of each other a group of formula-(A¹)_(o)-(A²)_(p)-(A³)_(q)-(A⁴)_(r)-R₁₀, in each occurrence o is 0 or1, p is 0 or 1, q is 0 or 1, r is 0 or 1, preferably o is 0 or 1 and pis 0 or 1 and q and r are 0;

R¹⁰ is H,

R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R^(a) and R^(b) are in eachoccurrence independently H, C₆-C₂₄aryl group which is unsubstituted orsubstituted by at least one group G, C₂-C₃₀ heteroaryl group which isunsubstituted or substituted by at least one group G, a C₁-C₂₅alkylgroup, which is unsubstituted or substituted by at least one group Eand/or interrupted by D, C₆-C₂₄ aryloxy group which is unsubstituted orsubstituted by at least one group G, or —SiR⁷⁰R⁷¹R⁷²; or

two groups R¹ and R² or R² and R³ or R³ and R⁴ of formula IV can formtogether the following ring system

wherein t is 1 to 5;

D is —CO—, —COO—, —S—, —SO—, —SO₂—, —O—, —CR⁶³═CR⁶⁴—, —NR⁶⁵—,—SiR⁷⁰R⁷¹—, —POR⁷²—, or —C≡C—,

E is —OR⁶⁹, —SR⁶⁹, —NR⁶⁵R⁶⁶, —COR⁶⁸, —COOR⁶⁷, —CONR⁶⁵R⁶⁶, —CN,—SiR⁷⁰R⁷¹R⁷², halogen, an unsubstituted C₆-C₂₄aryl group, a C₆-C₂₄arylgroup, which is substituted by F, C₁-C₁₈alkyl, C₁-C₁₈alkyl which isinterrupted by O, an unsubstituted C₂-C₃₀heteroaryl group, or aC₂-C₃₀heteroaryl group, which is substituted by F, C₁-C₁₈alkyl,C₁-C₁₈alkyl which is interrupted by O;

G is E, or a C₁-C₁₈alkyl group, or C₁-C₁₈alkyl which is interrupted byO,

R⁶³ and R⁶⁴ are independently of each other C₆-C₁₈aryl; C₆-C₁₈aryl whichis substituted by C₁-C₁₈alkyl, C₁-C₁₈alkoxy; C₁-C₁₈alkyl; or C₁-C₁₈alkylwhich is interrupted by —O—;

R⁶⁵ and R⁶⁶ are independently of each other a C₆-C₁₈aryl group; aC₆-C₁₈aryl which is substituted by C₁-C₁₈alkyl, or C₁-C₁₈alkoxy; aC₁-C₁₈alkyl group; or a C₁-C₁₈alkyl group, which is interrupted by —O—;or

R⁶⁵ and R⁶⁶ together form a five or six membered ring,

R⁶⁷ is a C₆-C₁₈aryl group; a C₆-C₁₈aryl group, which is substituted byC₁-C₁₈alkyl, or C₁-C₁₈alkoxy; a C₁-C₁₈alkyl group; or a C₁-C₁₈alkylgroup, which is interrupted by —O—,

R⁶⁸ is H; a C₆-C₁₈aryl group; a C₆-C₁₈aryl group, which is substitutedby C₁-C₁₈alkyl, or C₁-C₁₈alkoxy; a C₁-C₁₈alkyl group; or a C₁-C₁₈alkylgroup, which is interrupted by —O—,

R⁶⁹ is a C₆-C₁₈aryl; a C₆-C₁₈aryl, which is substituted by C₁-C₁₈alkyl,or C₁-C₁₈alkoxy; a C₁-C₁₈alkyl group; or a C₁-C₁₈alkyl group, which isinterrupted by —O—,

R⁷⁰ and R⁷¹ are independently of each other a C₁-C₁₈alkyl group, aC₆-C₁₈aryl group, or a C₆-C₁₈aryl group, which is substituted byC₁-C₁₈alkyl, and

R⁷² is a C₁-C₁₈alkyl group, a C₆-C₁₈aryl group, or a C₆-C₁₈aryl group,which is substituted by C₁-C₁₈alkyl,

wherein the following compound is excluded:

The combination of the Benzimidazolo[1,2-a]benzimidazol group havingdonor action with the nitril group having acceptor action gives rise tomaterials that are highly suitable in devices that emit green, or bluelight. Moreover, the improved ambipolar characteristics give rise tomore balanced charge transport in devices resulting in lower voltagesand higher external quantum efficiencies (EQE's).

One key finding of the inventors of the present invention is therelevance of the position of the nitrile group, which is not directlysubstituted at the benzimidazolo[1,2-a]benzimidazole skeleton, butsubstituted at the aromatic or heteroaromatic residue X⁴. Therefore, thecompounds of the present invention are characterized by a high acceptorstrength, efficient bipolar characteristics and a good suitability asTADF hosts or emitters.

The compounds of the present invention may be used forelectrophotographic photoreceptors, photoelectric converters, organicsolar cells (organic photovoltaics), switching elements, such as organictransistors, for example, organic FETs and organic TFTs, organic lightemitting field effect transistors (OLEFETs), image sensors, dye lasersand electroluminescent devices, such as, for example, organiclight-emitting diodes (OLEDs).

Accordingly, a further subject of the present invention is directed toan electronic device, comprising a compound according to the presentinvention. The electronic device is preferably an electroluminescentdevice, such as an organic light-emitting diode (OLED).

The compounds of formula I can in principal be used in any layer of anEL device, but are preferably used as host, charge transport and/orcharge/exciton blocking material. Particularly, the compounds of formulaI are used as host material for green, especially blue light emittingphosphorescent emitters. Additionally, the compounds of formula I areused as TADF emitter or TADF host materials in combination with at leastone fluorescent emitter, especially in OLEDs emitting in the blue andgreen region of the electromagnetic spectrum.

Hence, a further subject of the present invention is directed to acharge transport layer, comprising a compound of formula I according tothe present invention.

A further subject of the present invention is directed to an emittinglayer, comprising a compound of formula I according to the presentinvention. In said embodiment a compound of formula I is preferably usedas host material, more preferably in combination with a phosphorescentemitter.

A further subject of the present invention is directed to acharge/exciton blocking layer, comprising a compound of formula Iaccording to the present invention.

A further subject of the present invention is directed to an OLEDcomprising at least one compound of formula I as TADF emitter or TADFhost material in combination with at least one fluorescent emitter.

The terms halogen, alkyl, alkoxy, cycloalkyl, aryl, aryloxy, aralkyl,heteroaryl, arylene, heteroarylene generally have the following meaning,if said groups are not further specified in specific embodimentsmentioned below:

Halogen is fluorine, chlorine, bromine and iodine.

C₁-C₂₅alkyl (C₁-C₁₈alkyl) is typically linear or branched, wherepossible. Examples are methyl, ethyl, n-propyl, isopropyl, n-butyl,sec.-butyl, isobutyl, tert-butyl, n-pentyl, 2-pentyl, 3-pentyl,2,2-dimethylpropyl, 1,1,3,3-tetramethylpentyl, n-hexyl, 1-methylhexyl,1,1,3,3,5,5-hexamethylhexyl, n-heptyl, isoheptyl,1,1,3,3-tetramethylbutyl, 1-methylheptyl, 3-methylheptyl, n-octyl,1,1,3,3-tetramethylbutyl and 2-ethylhexyl, n-nonyl, decyl, undecyl,dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, oroctadecyl. C₁-C₈alkyl is typically methyl, ethyl, n-propyl, isopropyl,n-butyl, sec.-butyl, isobutyl, tert-butyl, n-pentyl, 2-pentyl, 3-pentyl,2,2-dimethyl-propyl, n-hexyl, n-heptyl, n-octyl,1,1,3,3-tetramethylbutyl and 2-ethylhexyl. C₁-C₄alkyl is typicallymethyl, ethyl, n-propyl, isopropyl, n-butyl, sec.-butyl, isobutyl,tert.-butyl.

C₁-C₂₅alkoxy groups (C₁-C₁₈alkoxy groups) are straight-chain or branchedalkoxy groups, e.g. methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy,sec-butoxy, tert-butoxy, amyloxy, isoamyloxy or tert-amyloxy, heptyloxy,octyloxy, isooctyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy,tetradecyloxy, pentadecyloxy, hexadecyloxy, heptadecyloxy andoctadecyloxy. Examples of C₁-C₈alkoxy are methoxy, ethoxy, n-propoxy,isopropoxy, n-butoxy, sec.-butoxy, isobutoxy, tert.-butoxy, n-pentyloxy,2-pentyloxy, 3-pentyloxy, 2,2-dimethylpropoxy, n-hexyloxy, n-heptyloxy,n-octyloxy, 1,1,3,3-tetramethylbutoxy and 2-ethylhexyloxy, preferablyC₁-C₄alkoxy such as typically methoxy, ethoxy, n-propoxy, isopropoxy,n-butoxy, sec.-butoxy, isobutoxy, tert.-butoxy.

The term “cycloalkyl group” is typically C₅-C₁₂cycloalkyl, such ascyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl,cyclodecyl, cycloundecyl, cyclododecyl, preferably cyclopentyl,cyclohexyl, cycloheptyl, or cyclooctyl, which may be unsubstituted orsubstituted.

C₆-C₂₄aryl (preferably C₆-C₁₈aryl), which optionally can be substituted,is typically phenyl, 4-methylphenyl, 4-methoxyphenyl, naphthyl,especially 1-naphthyl, or 2-naphthyl, biphenylyl, terphenylyl, pyrenyl,2- or 9-fluorenyl, phenanthryl, or anthryl, which may be unsubstitutedor substituted. Phenyl, 1-naphthyl and 2-naphthyl are examples of aC₆-C₁₀aryl group.

C₆-C₂₄aryloxy, which optionally can be substituted, is typicallyC₆-C₁₀aryloxy, which optionally can be substituted by one, or moreC₁-C₈alkyl and/or C₁-C₈alkoxy groups, such as, for example, phenoxy,1-naphthoxy, or 2-naphthoxy.

C₇-C₂₅aralkyl is typically benzyl, 2-benzyl-2-propyl, β-phenyl-ethyl,α,α-dimethylbenzyl, ω-phenyl-butyl, ω,ω-dimethyl-ω-phenyl-butyl,ω-phenyl-dodecyl, ω-phenyl-octadecyl, ω-phenyl-eicosyl orω-phenyl-docosyl, preferably C₇-C₁₈aralkyl such as benzyl,2-benzyl-2-propyl, β-phenyl-ethyl, α,α-dimethylbenzyl, ω-phenyl-butyl,ω,ω-dimethyl-ω-phenyl-butyl, ω-phenyl-dodecyl or ω-phenyl-octadecyl, andparticularly preferred C₇-C₁₂aralkyl such as benzyl, 2-benzyl-2-propyl,β-phenyl-ethyl, α,α-dimethylbenzyl, ω-phenyl-butyl, orω,ω-dimethyl-ω-phenyl-butyl, in which both the aliphatic hydrocarbongroup and aromatic hydrocarbon group may be unsubstituted orsubstituted. Preferred examples are benzyl, 2-phenylethyl,3-phenylpropyl, naphthylethyl, naphthylmethyl, and cumyl.

C₂-C₃₀heteroaryl (preferably C₂-C₁₃heteroarylaryl) represents a ringwith five to seven ring atoms or a condensed ring system, whereinnitrogen, oxygen or sulfur are the possible hetero atoms, and istypically a heterocyclic group with five to 30 atoms having at least sixconjugated π-electrons such as thienyl, benzothiophenyl,dibenzothiophenyl, thianthrenyl, furyl, furfuryl, 2H-pyranyl,benzofuranyl, isobenzofuranyl, dibenzofuranyl, phenoxythienyl, pyrrolyl,imidazolyl, pyrazolyl, pyridyl, bipyridyl, triazinyl, pyrimidinyl,pyrazinyl, pyridazinyl, indolizinyl, isoindolyl, indolyl, indazolyl,purinyl, quinolizinyl, chinolyl, isochinolyl, phthalazinyl,naphthyridinyl, chinoxalinyl, chinazolinyl, cinnolinyl, pteridinyl,carbazolyl, carbolinyl, benzotriazolyl, benzoxazolyl, phenanthridinyl,acridinyl, pyrimidinyl, phenanthrolinyl, phenazinyl, isothiazolyl,phenothiazinyl, isoxazolyl, furazanyl, 4-imidazo[1,2-a]benzimidazoyl,5-benzimidazo[1,2-a]benzimidazoyl,benzimidazolo[2,1-b][1,3]benzothiazolyl, carbazolyl, or phenoxazinyl,which can be unsubstituted or substituted.Benzimidazo[1,2-a]benzimidazo-5-yl, benzimidazo[1,2-a]benzimidazo-2-yl,carbazolyl and dibenzofuranyl are examples of a C₂-C₁₄heteroaryl group.

A C₂-C₁₃heteroaryl group is for example,benzimidazo[1,2-a]benzimidazo-5-yl

benzimidazo[1,2-a]benzimidazo-2-yl

benzimidazolo[2,1-b][1,3]benzothiazolyl,benzimidazolo[2,1-b][1,3]benzoxazole, carbazolyl, dibenzofuranyl, ordibenzothiophenyl, which can be unsubstituted or substituted, especiallyby C₆-C₁₀aryl, or C₆-C₁₀aryl, which is substituted by C₁-C₄alkyl; orC₂-C₁₃heteroaryl.

C₂-C₃₀heteroaryl (preferably C₂-C₁₃ heteroarylaryl) means that theheteroaryl residue comprises at least 2 carbon atoms and at most 30carbon atoms in the base skeleton (without substituents). The furtheratoms in the heteroaryl base skeleton are heteroatoms (N, O and/or S).

R^(24′) is in each case independently C₁-C₁₈alkyl, such as methyl,ethyl, n-propyl, iso-propyl, n-butyl, isobutyl, sec-butyl, hexyl, octyl,or 2-ethyl-hexyl, or C₆-C₁₄aryl, such as phenyl, tolyl, naphthyl,phenanthronyl, triphenylenyl, fluoranthenyl or biphenylyl.

C₆-C₂₄arylene groups, which optionally can be substituted by G, aretypically phenylene, 4-methylphenylene, 4-methoxyphenylene, naphthylene,especially 1-naphthylene, or 2-naphthylene, biphenylylene,terphenylylene, pyrenylene, 2- or 9-fluorenylene, phenanthrylene, oranthrylene, which may be unsubstituted or substituted. PreferredC₆-C₂₄arylen groups are 1,3-phenylene, 3,3′-biphenylylene,3,3′-m-terphenylene, 2- or 9-fluorenylene, phenanthrylene, which may beunsubstituted or substituted.

C₂-C₃₀heteroarylene groups, which optionally can be substituted by G,represent a ring with five to seven ring atoms or a condensed ringsystem, wherein nitrogen, oxygen or sulfur are the possible heteroatoms, and is typically a heterocyclic group with five to 30 atomshaving at least six conjugated-electrons such as thienylene,benzothiophenylene, dibenzothiophenylene, thianthrenylene, furylene,furfurylene, 2H-pyranylene, benzofuranylene, isobenzofuranylene,dibenzofuranylene, phenoxythienylene, pyrrolylene, imidazolylene,pyrazolylene, pyridylene, bipyridylene, triazinylene, pyrimidinylene,pyrazinylene, pyridazinylene, indolizinylene, isoindolylene, indolylene,indazolylene, purinylene, quinolizinylene, chinolylene, isochinolylene,phthalazinylene, naphthyridinylene, chinoxalinylene, chinazolinylene,cinnolinylene, pteridinylene, carbolinylene, benzotriazolylene,benzoxazolylene, phenanthridinylene, acridinylene, pyrimidinylene,phenanthrolinylene, phenazinylene, isothiazolylene, phenothiazinylene,isoxazolylene, furazanylene, carbazolylene,benzimidazo[1,2-a]benzimidazo-2,5-ylene, or phenoxazinylene, which canbe unsubstituted or substituted. Preferred C₂-C₃₀heteroarylen groups arepyridylene, triazinylene, pyrimidinylene, carbazolylene,dibenzofuranylene and benzimidazo[1,2-a]benzimidazo-2,5-ylene

which can be unsubstituted or substituted, especially by C₆-C₁₀aryl,C₆-C₁₀aryl which is substituted by C₁-C₄alkyl; or C₂-C₁₄heteroaryl.

Possible preferred substituents of the above-mentioned groups areC₁-C₈alkyl, a hydroxyl group, a mercapto group, C₁-C₈alkoxy,C₁-C₈alkylthio, halogen, halo-C₁-C₈alkyl, or a cyano group.

The C₆-C₂₄aryl (C₆-C₁₈aryl) and C₂-C₃₀heteroaryl groups are preferablysubstituted by one, or more C₁-C₈alkyl groups.

If a substituent occurs more than one time in a group, it can bedifferent in each occurrence.

Halo-C₁-C₈alkyl is an alkyl group where at least one of the hydrogenatoms is replaced by a halogen atom. Examples are —CF₃, —CF₂CF₃,—CF₂CF₂CF₃, —CF(CF₃)₂, —(CF₂)₃CF₃, and —C(CF₃)₃.

The wording “substituted by G” means that one, or more, especially oneto three substituents G might be present.

As described above, the aforementioned groups may be substituted by Eand/or, if desired, interrupted by D. Interruptions are of coursepossible only in the case of groups containing at least 2 carbon atomsconnected to one another by single bonds; C₆-C₁₈aryl is not interrupted;interrupted arylalkyl contains the unit D in the alkyl moiety.C₁-C₁₈alkyl substituted by one or more E and/or interrupted by one ormore units D is, for example, (CH₂CH₂O)₁₋₉—R^(x), where R^(x) is H orC₁-C₁₀alkyl or C₂-C₁₀alkanoyl (e.g. CO—CH(C₂H₅)C₄H₉),CH₂—CH(OR^(y′))—CH₂—O—R^(y), where R^(y) is C₁-C₁₈alkyl,C₆-C₁₂cycloalkyl, phenyl, C₇-C₁₅phenylalkyl, and R^(y′) embraces thesame definitions as R^(y) or is H;

C₁-C₈alkylene-COO—R^(z), e.g. CH₂COOR_(z), CH(CH₃)COOR^(z),C(CH₃)₂COOR^(z), where R^(z) is H, C₁-C₁₈alkyl, (CH₂CH₂O)₁₋₉—R^(x), andR^(x) embraces the definitions indicated above;

CH₂CH₂—O—CO—CH═CH₂; CH₂CH(OH)CH₂—O—CO—C(CH₃)═CH₂.

An alkyl group substituted by E is, for example, an alkyl group where atleast one of the hydrogen atoms is replaced by F. Examples are —CF₃,—CF₂CF₃,

—CF₂CF₂CF₃, —CF(CF₃)₂, —(CF₂)₃CF₃, and —C(CF₃)₃.

D is preferably —CO—, —COO—, —S—, —SO—, —SO₂—, —O—, —NR⁶⁵—, wherein R⁶⁵is C₁-C₁₈alkyl, such as methyl, ethyl, n-propyl, iso-propyl, n-butyl,isobutyl, or sec-butyl, or C₆-C₁₄aryl, such as phenyl, tolyl, naphthyl,or biphenylyl, or C₂-C₃₀heteroaryl, such as, for example,benzimidazo[1,2-a]benzimidazo-2-yl

carbazolyl, dibenzofuranyl, which can be unsubstituted or substitutedespecially by C₆-C₁₀aryl, or C₆-C₁₀aryl, which is substituted byC₁-C₄alkyl; or C₂-C₁₃heteroaryl.

E is —OR⁶⁹, —SR⁶⁹, —NR⁶⁵R⁶⁶, —COR⁶⁸, —COOR⁶⁷, —CONR⁶⁵R⁶⁶, —CN,—SiR⁷⁰R⁷¹R⁷²

E is preferably —OR⁶⁹; —SR⁶⁹; —NR⁶⁵R⁶⁶; —COR⁶⁸; —COOR⁶⁷; —CONR⁶⁵R⁶⁶; or—CN; wherein R⁶⁵, R⁶⁶, R⁶⁷, R⁶⁸ and R⁶⁹ are independently of each otherC₁-C₁₈alkyl, such as methyl, ethyl, n-propyl, iso-propyl, n-butyl,isobutyl, sec-butyl, hexyl, octyl, or 2-ethyl-hexyl, or C₆-C₁₄aryl, suchas phenyl, tolyl, naphthyl, or biphenylyl.

G is preferably —OR⁶⁹, —SR⁶⁹, —NR⁶⁵R⁶⁶; a C₁-C₁₈alkyl group, aC₆-C₁₄aryl group, a C₁-C₁₄aryl group, which is substituted by F, orC₁-C₁₈alkyl; a C₂-C₁₃heteroaryl group, or a C₂-C₁₃heteroaryl group,which is substituted by F, or C₁-C₁₈alkyl; wherein R⁶⁵, R⁶⁶ and R⁶⁹ areindependently of each other C₁-C₁₈alkyl, such as methyl, ethyl,n-propyl, iso-propyl, n-butyl, isobutyl, sec-butyl, hexyl, octyl, or2-ethyl-hexyl, or C₆-C₁₄aryl, such as phenyl, tolyl, naphthyl, orbiphenylyl.

Preferably, a, b, a′, b′, a″ and b″ have the following meanings:

a is 0, 1, 2 or 3,

b is 0, 1, 2 or 3,

and the sum of a+b is 1, 2 or 3, preferably, 1 or 2;

a′ and a″ are independently of each other 0, 1, 2 or 3,

b′ and b″ are independently of each other 0, 1, 2 or 3,

preferably, the sum of a′+b′ is 0, 1 or 2, more preferably 0 or 1,

preferably, the sum of a″+b″ is 0, 1 or 2, more preferably 0 or 1.

In one preferred embodiment, especially in the case that the compoundsof formula I are used TADF emitters or TADF host materials incombination with fluorescent emitters, a, a′ or a″ are preferably 0 or1, more preferably 0.

X⁴ is preferably a single bond or

preferably,

more preferably a single bond or

X² is O, S or NR⁶⁵, preferably X² is O, S, more preferably X² is O;

X⁵ is O, S or NR⁶⁵, preferably X⁵ is O, S, more preferably X⁵ is O.

X³ is preferably a single bond or a group of the following formula

R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ are in each occurrenceindependently H, C₆-C₂₄ aryl group which is unsubstituted or substitutedby at least one group G, C₂-C₃₀ heteroaryl group which is unsubstitutedor substituted by at least one group G, a C₁-C₂₅alkyl group, which isunsubstituted or substituted by at least one group E and/or interruptedby D, C₆-C₂₄ aryloxy group which is unsubstituted or substituted by atleast one group G, or —SiR⁷⁰R⁷¹R⁷²;

preferably, R¹, R², R⁴, R⁵, R⁶, R⁸ and R⁹ are H and R³ and R⁷ are ineach occurrence independently H, C₆-C₂₄ aryl group which isunsubstituted or substituted by at least one group G, C₂-C₃₀ heteroarylgroup which is unsubstituted or substituted by at least one group G, aC₁-C₂₅alkyl group, which is unsubstituted or substituted by at least onegroup E and/or interrupted by D, C₆-C₂₄ aryloxy group which isunsubstituted or substituted by at least one group G, or —SiR⁷⁰R⁷¹R⁷²;more preferably, R¹, R², R⁴, R⁵, R⁶, R⁸ and R⁹ are H and R³ and R⁷ arein each occurrence independently H or a group of the following formula:

or —SiR⁷⁰R⁷¹R⁷².

R⁷⁰ and R⁷¹ are independently of each other a C₁-C₁₈alkyl group, aC₆-C₁₈aryl group, or a C₆-C₁₈aryl group, which is substituted byC₁-C₁₈alkyl, and

R⁷² is a C₁-C₁₈alkyl group, a C₆-C₁₈aryl group, or a C₆-C₁₈aryl group,which is substituted by C₁-C₁₈alkyl; preferably, R⁷⁰, R⁷¹ and R⁷² arephenyl.

Preferably, o is in each occurrence 0 or 1 and p is 0 or 1 and q and rare 0, more preferably, o is 0 or 1 and p, q and r are 0.

A¹, A², A³, A⁴ are preferably in each occurrence independently of eachother a group of the formula:

preferably

preferably

wherein (C)— has the meaning that the bonding site of the group A¹, A²,A³ or A⁴ is linked to a C-atom, and (N)— has the meaning that thebonding site of the group A¹, A², A³ or A⁴ is linked to a N-atom.

R¹⁰ is preferably H or a group of the following formula:

preferably

preferably

preferably

preferably

preferably

preferably

Specific examples of the compounds represented by the formula (I) aregiven below. The compounds represented by the formula (I) are notlimited to the following specific examples.

Among the compounds of formula (I), more preferred compounds are:

Compounds of formula

wherein R³, R⁷, X³ and X⁴ are defined above and below.

Compounds of formula

wherein R⁷, X³, X¹, a and b are defined above and below.

Compounds of formula

wherein X³, X¹, a and b are defined above and below.

Compounds of formula

wherein c and d are 0 or 1, and the sum of c+d is 1 or 2;

R^(c) and R^(d) are CN;

and x and y are 0 or 1, and the sum of x+y is 1 or 2,

preferably, c is 1 and d is 0 and x is 0 and y is 1.

Preferably, in the compounds of formula (Ia):

R³, R⁷ are independently of each other H or a group of the followingformula:

or —SiR⁷⁰R⁷¹R⁷²,

R⁷⁰ and R⁷¹ are independently of each other a C₁-C₁₈alkyl group, aC₆-C₁₈aryl group, or a C₆-C₁₈aryl group, which is substituted byC₁-C₁₈alkyl, and

R⁷² is a C₁-C₁₈alkyl group, a C₆-C₁₈aryl group, or a C₆-C₁₈aryl group,which is substituted by C₁-C₁₈alkyl; preferably, R⁷⁰, R⁷¹ and R⁷² arephenyl.

Preferably, in the compounds of formula (Ia):

X³ is a single bond or a group of the following formula

Preferably, in the compounds of formula (Ia):

X⁴ is a single bond or

In the compounds of formula (Ib), the residues and indices preferablyhave the following meaning:

a is 0 or 1 and is b 0 or 1, whereby the sum of a and b is at least 1;

X¹ is preferably a group of the following formula:

X³ is a single bond or a group of the following formula:

and

R⁷ is H or group of the following formula:

or —SiR⁷⁰R⁷¹R⁷²,

R⁷⁰ and R⁷¹ are independently of each other a C₁-C₁₈alkyl group, aC₆-C₁₈aryl group, or a C₆-C₁₈aryl group, which is substituted byC₁-C₁₈alkyl, and

R⁷² is a C₁-C₁₈alkyl group, a C₆-C₁₈aryl group, or a C₆-C₁₈aryl group,which is substituted by C₁-C₁₈alkyl; preferably, R⁷⁰, R⁷¹ and R⁷² arephenyl.

More preferably, the compounds of formula (Ib) are compounds of formula(Ib′)

wherein R⁷ is defined above and below; and

R²¹, R²², R²³, R²⁴ and R²⁵

are CN,

preferably CN,

wherein at least one of the residues R²¹, R²², R²³, R²⁴ and R²⁵ is CN,preferably 1, 2 or 3, more preferably, 1 or 2 of the residues R²¹, R²²,R²³, R²⁴ and R²⁵ are CN.

In the compounds of formula (Ic), the residues and indices preferablyhave the following meaning:

a is 0 or 1 and is b 0 or 1, whereby the sum of a and b is at least 1;

X¹ is preferably a group of the following formula:

X³ is a single bond or a group of the following formula:

More preferably, the compounds of formula (Ic) have the compound offormula (Ic′)

wherein X³ is a single bond or a group of the following formula:

preferably, X³ is

and

R²¹, R²², R²³, R²⁴ and R²⁵

are CN,

preferably CN,

wherein at least one of the residues R²¹, R²², R²³, R²⁴ and R²⁵ is CN,preferably 1, 2 or 3, more preferably, 1 or 2 of the residues R²¹, R²²,R²³, R²⁴ and R²⁵ are CN.

More preferably, the compounds of formula (Id) have the compound offormula (Id′)

wherein

R¹, R⁷ or R⁸ are H,

wherein at least one of R¹, R⁷ or R⁸ is

and

R², R³ or R⁶ are H or CN, wherein at least one of R², R³ or R⁶ is CN.

Preferred compounds of formulae (Ib′), (Ic′) and (Id′) are mentioned inthe following tables:

Nr. R21 R22 R23 R24 R25 X³ CN CN H H H — CN H CN H H — CN H H CN H — CNH H H CN — CN H H H H — H CN CN H H — H CN H CN H — H CN H H CN — CN CNH H H Sp1 CN H CN H H Sp1 CN H H CN H Sp1 CN H H H CN Sp1 H CN CN H HSp1 H CN H CN H Sp1 H CN H H CN Sp1 CN Ar1 H H H — CN H Ar1 H H — CN H HAr1 H — CN H H H Ar1 — CN Ar2 H H H — CN H Ar2 H H — CN H H Ar2 H — CN HH H Ar2 — CN Ar3 H H H — CN H Ar3 H H — CN H H Ar3 H — CN H H H Ar3 — CNAr4 H H H — CN H Ar4 H H — CN H H Ar4 H — CN H H H Ar4 — CN H H H H — HCN CN H Ar1 — Ar1 CN CN H H — H CN CN H Ar3 Sp1 Ar3 CN CN H H Sp1 CN Ar3H H H Sp1 CN Ar5 H H H — CN H Ar5 H H — CN H H Ar5 H — CN H H H Ar5 —

Nr. R²¹ R²² R²³ R²⁴ R²⁵ R⁷ CN CN H H H Ar2 CN H CN H H Ar2 CN H H CN HAr2 CN H H H CN Ar2 CN H H H H Ar2 H CN CN H H Ar2 H CN H CN H Ar2 H CNH H CN Ar2 CN CN H H H Ar2 CN H CN H H Ar2 CN H H CN H Ar2 CN H H H CNAr2 H CN CN H H Ar2 H CN H CN H Ar2 H CN H H CN Ar2 CN Ar1 H H H Ar1 CNH Ar1 H H Ar1 CN H H Ar1 H Ar1 CN H H H Ar1 Ar1 CN Ar2 H H H Ar2 CN HAr2 H H Ar2 CN H H Ar2 H Ar2 CN H H H Ar2 Ar2 CN Ar3 H H H Ar3 CN H Ar3H H Ar3 CN H H Ar3 H Ar3 CN H H H Ar3 Ar3 CN Ar4 H H H Ar4 CN H Ar4 H HAr4 CN H H Ar4 H Ar4 CN H H H Ar4 Ar4 H CN CN H Ar1 Ar1 Ar1 CN CN H HAr1 H CN CN H Ar3 Ar3 Ar3 CN CN H H Ar3 CN Ar5 H H H Ar2 CN H Ar5 H HAr2 CN H H Ar5 H Ar2 CN H H H Ar5 Ar2

Nr. R¹ R² R³ R⁶ R⁷ R⁸ H H CN H H

H CN H H

CN H H H

CN H H

H

H H CN

H

CN H H

H

H H CN

H

H H CN

H

CN H H

H

Further specific examples of formula (I) are the following compounds:

The specific aryl-nitrile or heteroaryl-nitrilebenzimidazolo[1,2-a]benzimidazoles derivatives of the present inventionare found to be suitable for use in organo-electroluminescent devices.In particular, certain aryl-nitrile or heteroaryl-nitrilebenzimidazolo[1,2-a]benzimidazoles derivatives are suitable hostmaterials, especially host materials for phosphorescent emitters, chargetransport materials and/or charge/exciton blocker materials with goodefficiency and durability.

Also, said aryl-nitrile or heteroaryl-nitrilebenzimidazolo[1,2-a]benzimidazoles show low singlet triplet splitting,which makes them useful as TADF (Thermally Activated DelayedFluorescence, Adv. Mater. 2014, 26, 7931-7958) emitter or TADF hostmaterials in combination with fluorescent emitters. The TADF emitter orTADF host materials can be used together with one or more additionalhost materials.

The combination of the benzimidazolo[1,2-a]benzimidazole groups with thecyano group in the specific position of thebenzimidazolo[1,2-a]benzimidazole gives rise to materials that arehighly suitable in devices that emit green, or blue light. Moreover, theimproved ambipolar characteristics give rise to more balanced chargetransport in devices resulting in lower voltages and higher externalquantum efficiencies (EQE's).

One key finding of the inventors of the present invention is therelevance of the position of the nitrile group, which is not directlysubstituted at the benzimidazolo[1,2-a]benzimidazole skeleton, butsubstituted at the aromatic or heteroaromatic residue X4. Therefore, thecompounds of the present invention are characterized by a high acceptorstrength, efficient bipolar characteristics and a good suitability asTADF hosts or emitters.

The compounds of the present invention may be used forelectrophotographic photoreceptors, photoelectric converters, organicsolar cells (organic photovoltaics), switching elements, such as organictransistors, for example, organic FETs and organic TFTs, organic lightemitting field effect transistors (OLEFETs), image sensors, dye lasersand electroluminescent devices (EL devices), such as, for example,organic light-emitting diodes (OLEDs). Preferably, the compounds of thepresent invention are used in electroluminescent devices, especially inOLEDs.

Accordingly, a further subject of the present invention is directed toan electronic device, comprising a compound according to the presentinvention. The electronic device is preferably an electroluminescentdevice (EL-device), especially an OLED.

The compounds of formula I can in principal be used in any layer of anEL device, but are preferably used as host, charge transport and/orcharge/exciton blocking material. Particularly, the compounds of formulaI are used as host material for green, especially blue light emittingemitters, which are preferably phosphorescent emitters.

Hence, a further subject of the present invention is directed to acharge transport layer comprising a compound of formula I according tothe present invention.

A further subject of the present invention is directed to an emittinglayer, comprising a compound of formula I according to the presentinvention. In said embodiment a compound of formula I is preferably usedas host material in combination with an emitter, which is preferably aphosphorescent emitter.

A further subject of the present invention is directed to acharge/exciton blocking layer, comprising a compound of formula Iaccording to the present invention.

Synthesis of the Compounds of Formula (I)

Base Skeleton

The synthesis of the compounds of formula (I) can be carried out inanalogy to the synthesis of benzimidazolo[1,2-a]benzimidazoles mentionedin the prior art.

The synthesis of

is described, for example, in Achour, Reddouane; Zniber, Rachid,Bulletin des Societes Chimiques Belges 96 (1987) 787-92.

N-Arylation

The introduction of the group —X³—X⁴—CN (N-arylation) is generallycarried out by reacting the base skeleton

with a group Hal-X³—X⁴—CN, wherein Hal is F, Cl, Br or I, preferably F,Br or I. Suitable groups X³ and X⁴ are mentioned before.

The nucleophilic aromatic substitution (N-arylation) of

with F—X³—X⁴—CN is generally performed in the presence of a base (Angew.Chem. 2012, 124, 8136-8140, Angew. Chem. Int. Ed. 2008, 47, 8104-8107).Suitable bases are known to those skilled in the art and are preferablyselected from the group consisting of alkali metal alkali metal andalkaline earth metal hydroxides such as NaOH, KOH, Ca(OH)₂, alkali metalhydrides such as NaH, KH, alkali metal amides such as NaNH₂, alkalimetal or alkaline earth metal carbonates such as K₂CO₃ or Cs₂CO₃,alkaline metal phosphates such as K₃PO₄ alkaline metal fluorides such asKF, CsF and alkali metal alkoxides such as NaOMe, NaOEt. In addition,mixtures of the aforementioned bases are suitable. K₂CO₃ or Cs₂CO₃,K₃PO₄ are preferred.

The nucleophilic aromatic substitution (N-arylation) can be performed insolvent or in a melt. Preferably, the reaction is carried out in asolvent. Suitable solvents are, for example, (polar) aprotic solventssuch as dimethyl sulfoxide (DMSO), dimethylformamide (DMF),N-methyl-2-pyrrolidone (NMP) or dimethylacetamide (DMA).

The reaction temperature is strongly dependent on the reactivity of thearyl fluoride. The reaction (N-arylation) is preferably carried out at atemperature of −10 to 220° C., more preferably 60 to 150° C.

Ullmann reaction (N-arylation) of

with Y—X—X⁴—CN (Y is Cl, Br, or I) generally performed in the presenceof a base and a catalyst.

Reaction conditions for Ullmann reactions are, for example, described inAngew Chem Int Ed Engl., 48 (2009) 6954-71 WO14009317, WO12130709, J.Am. Chem. Soc. 131 (2009) 2009-2251, J. Org. Chem, 70 (2005) 5165.

Typically the Ullmann coupling of the compound of formula

with a compound of formula Y—X³—X⁴—CN (Y is Cl, Br, or I, especially Br,I very especially I) is done in the presence of copper, or a coppersalt, such as, for example, CuI, CuBr, Cu₂O, or CuO, and a ligand, suchas, for example, L-proline, trans-cyclohexane-1,2-diamine (DACH),1,10-phenanthroline in a solvent, such as, for example,dimethylsulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide(DMA), N-methylpyrrolidone (NMP) and dioxane, or a solvent mixture. Thereaction temperature is dependent on the reactivity of the startingmaterials, but is generally in the range of 25 to 200° C. If copper saltare used without a ligand the reaction temperatures are higher.

The N-arylation is, for example, disclosed in H. Gilman and D. A.Shirley, J. Am. Chem. Soc. 66 (1944) 888; D. Li et al., Dyes andPigments 49 (2001) 181-186 and Eur. J. Org. Chem. (2007) 2147-2151.

An example for an N-arylation of the

skeleton by copper-catalyzed coupling is shown in the following (seealso Example 18 in the Example part):

DACH is (±)-trans-1,2-diaminocyclohexane

Hal-X³—X⁴—CN

The synthesis of

is described, for example, in Achour, Reddouane; Zniber, Rachid,Bulletin des Societes Chimiques Belges 96 (1987) 787-92 and WO12130709.

The groups Hal-X³—X⁴—CN are commercially available or prepared byprocesses known in the art. Suitable preparation processes fore somegroups Hal-X³—X⁴—CN are mentioned in the following.

Suitable base skeletons of the formula

are either commercially available (especially in the cases when X is S,O, NH), or can be obtained by processes known to those skilled in theart. Reference is made to WO2010079051 and EP1885818.

The halogenation of said base skeletons

(carbazole, dibenzofuran or dibenzothiophene, which is unsubstituted orsubstituted) can be performed by methods known to those skilled in theart. Preference is given to brominating or iodinating in the 3 and 6positions (dibromination, diiodation or mixed bromination/iodation) orin the 3 or 6 positions (monobromination, monoiodation) of the baseskeleton in the case of carbazole, respectively in the 2 and 8 positions(dibromination, diiodation) or in the 2 or 8 positions (monobromination,monoiodation) of the base skeleton in the case of dibenzofuran anddibenzothiophene.

Optionally substituted dibenzofurans, dibenzothiophenes and carbazolescan be dibrominated in the 2,8 positions (dibenzofuran anddibenzothiophene) or 3,6 positions (carbazole) with bromine or NBS inglacial acetic acid or in chloroform. For example, the bromination withBr₂ can be effected in glacial acetic acid or chloroform at lowtemperatures, e.g. 0° C. Suitable processes are described, for example,in M. Park, J. R. Buck, C. J. Rizzo, Tetrahedron, 54 (1998) 12707-12714for X=NPh, and in W. Yang et al., J. Mater. Chem. 13 (2003) 1351 forX=S. In addition, 3,6-dibromocarbazole, 3,6-dibromo-9-phenylcarbazole,2,8-dibromodibenzothiophene, 2,8-dibromodibenzofuran, 2-bromocarbazole,3-bromodibenzothiophene, 3-bromodibenzofuran, 3-bromocarbazole,2-bromodibenzothiophene and 2-bromodibenzofuran are commerciallyavailable.

Monobromination in the 4 position of dibenzofuran (and analogously fordibenzothiophene) is described, for example, in J. Am. Chem. Soc. 1984,106, 7150. Dibenzofuran (dibenzothiophene) can be monobrominated in the3 position by a sequence known to those skilled in the art, comprising anitration, reduction and subsequent Sandmeyer reaction.

Monobromination in the 2 position of dibenzofuran or dibenzothiopheneand monobromination in the 3 position of carbazole are effectedanalogously to the dibromination, with the exception that only oneequivalent of bromine or NBS is added.

For the nucleophilic substitution, Cl- or F-substituted dibenzofurans,dibenzothiophenes and carbazoles are preferred. The chlorination isdescribed, inter alia, in J. Heterocyclic Chemistry, 34 (1997) 891-900,Org. Lett., 6 (2004) 3501-3504; J. Chem. Soc. [Section] C: Organic, 16(1971) 2775-7, Tetrahedron Lett. 25 (1984) 5363-6, J. Org. Chem. 69(2004) 8177-8182. The fluorination is described in J. Org. Chem. 63(1998) 878-880 and J. Chem. Soc., Perkin Trans. 2, 5 (2002) 953-957.

Introduction of the

Skeleton

The introduction of the

skeleton, can be affected, for example, by copper-catalyzed coupling(Ullmann reaction). Suitable reaction components and reaction conditionsfor carrying out the Ullmann reaction are mentioned above.

Examples for a copper catalyzed coupling are (see also Example 7B and 8Ain the Example part):

DACH is (±)-trans-1,2-diaminocyclohexane

Alternatively, the introduction of the

skeleton, especially in cases, wherein the

skeleton is substituted, e.g. by a group

can be affected, for example, by Pd catalyzed coupling of diboronic acidor diboronate group containing dibenzofurans, dibenzothiophenes orcarbazoles with halogenated aromatic groups, wherein the halogen ispreferably I (Suzuki coupling).

Examples for a Pd catalyzed coupling are (see also Examples 9B and 10Bin the Example part):

Diboronic acid or diboronate group containing dibenzofurans,dibenzothiophenes and carbazoles can be readily prepared by anincreasing number of routes. An overview of the synthetic routes is, forexample, given in Angew. Chem. Int Ed. 48 (2009) 9240-9261.

By one common route diboronic acid or diboronate group containingdibenzofurans, dibenzothiophenes, and carbazoles can be obtained byreacting halogenated dibenzofurans dibenzothiophenes and carbazoles with(Y¹O)₂B—B(OY¹)₂,

in the presence of a catalyst, such as, for example,[1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II), complex(Pd(Cl)₂(dppf)), and a base, such as, for example, potassium acetate, ina solvent, such as, for example, dimethyl formamide, dimethyl sulfoxide,dioxane and/or toluene (cf. Prasad Appukkuttan et al., Synlett 8 (2003)1204), wherein Y¹ is independently in each occurrence a C₁-C₁₈alkylgroup and Y² is independently in each occurrence a C₂-C₁₀alkylene group,such as —CY³Y⁴—CY⁵Y⁶—, or —CY⁷Y⁸—CY⁹Y¹⁰—CY¹¹Y¹²—, wherein Y³, Y⁴, Y⁵,Y⁶, Y⁷, Y⁸, Y⁹, Y¹⁰, Y¹¹ and Y¹² are independently of each otherhydrogen, or a C₁-C₁₈alkyl group, especially —C(CH₃)₂C(CH₃)₂—,—C(CH₃)₂CH₂C(CH₃)₂—, or —CH₂C(CH₃)₂CH₂—, and Y¹³ and Y¹⁴ areindependently of each other hydrogen, or a C₁-C₁₈alkyl group.

Diboronic acid or diboronate group containing dibenzofurans,dibenzothiophenes and carbazoles can also be prepared by reactinghalogenated dibenzofurans, dibenzothiophenes and carbazoles with alkyllithium reagents, such as, for example, n-butyl lithium, or t-buthyllithium, followed by reaction with boronic esters, such as, for example,B(isopropoxy)₃, B(methoxy)₃, or

(cf. Synthesis (2000) 442-446).

Diboronic acid or diboronate group containing dibenzofurans,dibenzothiophenes and carbazoles can also be prepared by reactingdibenzofurans, dibenzothiophenes and carbazoles with lithium amides,such as, for example, lithium diisopropylamide (LDA) followed byreaction with boronic esters such as, for example, B(isopropoxy)₃,B(methoxy)₃, or

J. Org. Chem. 73 (2008) 2176-2181).

Compounds of Formula I in Organic Electronics Application

It has been found that the compounds of the formula I are particularlysuitable for use in applications in which charge carrier conductivity isrequired, especially for use in organic electronics applications, forexample selected from switching elements such as organic transistors,e.g. organic FETs and organic TFTs, organic solar cells and organiclight-emitting diodes (OLEDs).

The organic transistor generally includes a semiconductor layer formedfrom an organic layer with charge transport capacity; a gate electrodeformed from a conductive layer; and an insulating layer introducedbetween the semiconductor layer and the conductive layer. A sourceelectrode and a drain electrode are mounted on this arrangement in orderthus to produce the transistor element. In addition, further layersknown to those skilled in the art may be present in the organictransistor. The layers with charge transport capacity may comprise thecompounds of formula I.

The organic solar cell (photoelectric conversion element) generallycomprises an organic layer present between two plate-type electrodesarranged in parallel. The organic layer may be configured on a comb-typeelectrode. There is no particular restriction regarding the site of theorganic layer and there is no particular restriction regarding thematerial of the electrodes. When, however, plate-type electrodesarranged in parallel are used, at least one electrode is preferablyformed from a transparent electrode, for example an ITO electrode or afluorine-doped tin oxide electrode. The organic layer is formed from twosublayers, i.e. a layer with p-type semiconductor properties or holetransport capacity, and a layer formed with n-type semiconductorproperties or charge transport capacity. In addition, it is possible forfurther layers known to those skilled in the art to be present in theorganic solar cell. The layers with charge transport capacity maycomprise the compounds of formula I.

The compounds of the formula I being particularly suitable in OLEDs foruse as matrix material in a light-emitting layer and/or as electronand/or exciton blocker material and/or as hole and/or exciton blockermaterial and/or charge transport materials, especially in combinationwith a phosphorescence emitter.

In the case of use of the inventive compounds of the formula I in OLEDs,OLEDs which have good efficiencies and a long lifetime and which can beoperated especially at a low use and operating voltage are obtained. Theinventive compounds of the formula I are suitable especially for use asmatrix and/or charge/exciton blocker materials for blue and greenemitters, for example light blue or deep blue emitters, these beingespecially phosphorescence emitters. Furthermore, the compounds of theformula I can be used as conductor/complementary materials in organicelectronics applications selected from switching elements and organicsolar cells.

In the emission layer or one of the emission layers of an OLED, it isalso possible to combine an emitter material with at least one matrixmaterial of the compound of the formula I and one or more further matrixmaterials. This may achieve a high quantum efficiency of this emissionlayer.

It is likewise possible that the compounds of the formula I are presentboth in the light-emitting layer (preferably as matrix material) and inthe blocking layers (as charge/exciton blockers).

When a compound of the formula I is used as matrix (host) material in anemission layer and additionally as charge/exciton blocker material,owing to the chemical identity or similarity of the materials, animproved interface between the emission layer and the adjacentcharge/exciton blocker material, which can lead to a decrease in thevoltage with equal luminance and to an extension of the lifetime of theOLED. Moreover, the use of the same material for charge/exciton blockermaterial and for the matrix of an emission layer allows the productionprocess of an OLED to be simplified, since the same source can be usedfor the vapor deposition process of the material of one of the compoundsof the formula I.

Also, the compounds of the formula I show low singlet triplet splitting,which makes them useful as TADF (Thermally Activated DelayedFluorescence, Adv. Mater. 2014, 26, 7931-7958) emitter or TADF hostmaterials in combination with fluorescent emitters. Therefore, thecompounds of the formula I being particularly suitable in OLEDs for useas TADF emitters or TADF host materials together with a fluorescentemitter. The TADF emitters or TADF host materials is preferably usedtogether with one or more additional host materials.

Suitable structures of organic electronic diodes are known to thoseskilled in the art and are specified below.

The present invention further provides an organic light-emitting diodecomprising an anode (a) and a cathode (i) and a light-emitting layer (e)arranged between the anode (a) and the cathode (i), and if appropriateat least one further layer selected from the group consisting of atleast one blocking layer for holes/excitons, at least one blocking layerfor electrons/excitons, at least one hole injection layer, at least onehole transport layer, at least one electron injection layer and at leastone electron transport layer, wherein the at least one compound of theformula I is present in the light-emitting layer (e) and/or in at leastone of the further layers. The at least one compound of the formula I ispreferably present in the light-emitting layer and/or the charge/excitonblocking layers.

In a preferred embodiment of the present invention, at least onecompound of the formula I is used as charge transport material. Examplesof preferred compounds of formula I are shown above.

Compounds carrying at least one of the following groups are for exampleparticularly useful hole transport materials:

Further preferably, compounds of formula I which are particularly usefulhole transport materials comprise one nitrile group.

Compounds carrying more than one nitrile group and onebenzimidazolo[1,2-a]benzimidazole group are particularly useful aselectron transport materials.

In another preferred embodiment of the present invention, at least onecompound of the formula I is used as charge/exciton blocker material.

The present application further relates to a light-emitting layercomprising at least one compound of the formula I, preferably as hostmaterial. Examples of preferred compounds of formula I are shown above.The following compounds are examples for particularly useful compoundsin the light-emitting layer, especially as host material:

Examples for compounds of formula I particularly suitable as hostmaterial for phosphorescence emitters, especially for phosphorescenceemitters emitting in the blue or green area of the visibleelectromagnetic spectrum:

Examples for compounds of formula I particularly suitable as TADF hostmaterial, especially for TADF based OLEDs emitting in the blue or greenarea of the visible electromagnetic spectrum:

Structure of the Inventive OLED

The inventive organic light-emitting diode (OLED) thus generally has thefollowing structure: an anode (a) and a cathode (i) and a light-emittinglayer (e) arranged between the anode (a) and the cathode (i).

The inventive OLED may, for example—in a preferred embodiment—be formedfrom the following layers:

1. Anode (a)

2. Hole transport layer (c)

3. Light-emitting layer (e)

4. Blocking layer for holes/excitons (f)

5. Electron transport layer (g)

6. Cathode (i)

Layer sequences different than the aforementioned structure are alsopossible, and are known to those skilled in the art. For example, it ispossible that the OLED does not have all of the layers mentioned; forexample, an OLED with layers (a) (anode), (e) (light-emitting layer) and(i) (cathode) is likewise suitable, in which case the functions of thelayers (c) (hole transport layer) and (f) (blocking layer forholes/excitons) and (g) (electron transport layer) are assumed by theadjacent layers. OLEDs which have layers (a), (c), (e) and (i), orlayers (a), (e), (f), (g) and (i), are likewise suitable. In addition,the OLEDs may have a blocking layer for electrons/excitons (d) betweenthe hole transport layer (c) and the Light-emitting layer (e).

It is additionally possible that a plurality of the aforementionedfunctions (electron/exciton blocker, hole/exciton blocker, holeinjection, hole conduction, electron injection, electron conduction) arecombined in one layer and are assumed, for example, by a single materialpresent in this layer. For example, a material used in the holetransport layer, in one embodiment, may simultaneously block excitonsand/or electrons.

Furthermore, the individual layers of the OLED among those specifiedabove may in turn be formed from two or more layers. For example, thehole transport layer may be formed from a layer into which holes areinjected from the electrode, and a layer which transports the holes awayfrom the hole-injecting layer into the light-emitting layer. Theelectron transport layer may likewise consist of a plurality of layers,for example a layer in which electrons are injected by the electrode,and a layer which receives electrons from the electron injection layerand transports them into the light-emitting layer. These layersmentioned are each selected according to factors such as energy level,thermal resistance and charge carrier mobility, and also energydifference of the layers specified with the organic layers or the metalelectrodes. The person skilled in the art is capable of selecting thestructure of the OLEDs such that it is matched optimally to the organiccompounds used in accordance with the invention.

In a preferred embodiment the OLED according to the present inventioncomprises in this order:

(a) an anode,

(b) optionally a hole injection layer,

(c) optionally a hole transport layer,

(d) optionally an exciton blocking layer

(e) an emitting layer,

(f) optionally a hole/exciton blocking layer

(g) optionally an electron transport layer,

(h) optionally an electron injection layer, and

(i) a cathode.

In a particularly preferred embodiment the OLED according to the presentinvention comprises in this order:

(a) an anode,

(b) optionally a hole injection layer,

(c) a hole transport layer,

(d) an exciton blocking layer

(e) an emitting layer,

(f) a hole/exciton blocking layer

(g) an electron transport layer, and

(h) optionally an electron injection layer, and

(i) a cathode.

The properties and functions of these various layers, as well as examplematerials are known from the prior art and are described in more detailbelow on basis of preferred embodiments.

Anode (a):

The anode is an electrode which provides positive charge carriers. Itmay be composed, for example, of materials which comprise a metal, amixture of different metals, a metal alloy, a metal oxide or a mixtureof different metal oxides. Alternatively, the anode may be a conductivepolymer. Suitable metals comprise the metals of groups 11, 4, 5 and 6 ofthe Periodic Table of the Elements, and also the transition metals ofgroups 8 to 10. When the anode is to be transparent, mixed metal oxidesof groups 12, 13 and 14 of the Periodic Table of the Elements aregenerally used, for example indium tin oxide (ITO). It is likewisepossible that the anode (a) comprises an organic material, for examplepolyaniline, as described, for example, in Nature, Vol. 357, pages 477to 479 (Jun. 11, 1992). Preferred anode materials include conductivemetal oxides, such as indium tin oxide (ITO) and indium zinc oxide(IZO), aluminum zinc oxide (AlZnO), and metals. Anode (and substrate)may be sufficiently transparent to create a bottom-emitting device. Apreferred transparent substrate and anode combination is commerciallyavailable ITO (anode) deposited on glass or plastic (substrate). Areflective anode may be preferred for some top-emitting devices, toincrease the amount of light emitted from the top of the device. Atleast either the anode or the cathode should be at least partlytransparent in order to be able to emit the light formed. Other anodematerials and structures may be used.

Hole Injection Layer (b):

Generally, injection layers are comprised of a material that may improvethe injection of charge carriers from one layer, such as an electrode ora charge generating layer, into an adjacent organic layer. Injectionlayers may also perform a charge transport function. The hole injectionlayer may be any layer that improves the injection of holes from anodeinto an adjacent organic layer. A hole injection layer may comprise asolution deposited material, such as a spin-coated polymer, or it may bea vapor deposited small molecule material, such as, for example, CuPc orMTDATA. Polymeric hole-injection materials can be used such aspoly(N-vinylcarbazole) (PVK), polythiophenes, polypyrrole, polyaniline,self-doping polymers, such as, for example, sulfonatedpoly(thiophene-3-[2[(2-methoxyethoxy)ethoxy]-2,5-diyl) (Plexcore® OCConducting Inks commercially available from Plextronics), and copolymerssuch as poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) alsocalled PEDOT/PSS.

Hole Transport Layer (c):

Either hole-transporting molecules or polymers may be used as the holetransport material. Suitable hole transport materials for layer (c) ofthe inventive OLED are disclosed, for example, in Kirk-OthmerEncyclopedia of Chemical Technology, 4th Edition, Vol. 18, pages 837 to860, 1996, US20070278938, US2008/0106190, US2011/0163302 (triarylamineswith (di)benzothiophen/(di)benzofuran; Nan-Xing Hu et al. Synth. Met.111 (2000) 421 (indolocarbazoles), WO2010002850 (substituted phenylaminecompounds) and WO2012/16601 (in particular the hole transport materialsmentioned on pages 16 and 17 of WO2012/16601). Combination of differenthole transport material may be used. Reference is made, for example, toWO2013/022419, wherein

constitute the hole transport layer.

Customarily used hole-transporting molecules are selected from the groupconsisting of

(4-phenyl-N-(4-phenylphenyl)-N-[4-[4-(N-4-(4-phenyl-phenyl)phenyl]anilino)phenyl]phenyl]aniline),

(4-phenyl-N-(4-phenylphenyl)-N-[4-[4-(4-phenyl-N-(4-phenylphenyl)anilino)phenyl]phenyl]aniline),

(4-phenyl-N-[4-(9-phenylcarbazol-3-yl)phenyl]-N-(4-phenylphenyl)aniline),

(1,1′,3,3′-tetraphenylspiro[1,3,2-benzodiazasilole-2,2′-3a,7a-dihydro-1,3,2-benzodiazasilole]),

(N2,N2,N2′,N2′,N7,N7,N7′,N7′-octakis(p-tolyl)-9,9′-spirobi[fluorene]-2,2′,7,7′-tetramine),4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (α-NPD),N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine(TPD), 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC),N,N′-bis(4-methylphenyl)-N,N′-bis(4-ethylphenyl)-[1,1′-(3,3′-dimethyl)biphenyl]-4,4′-diamine(ETPD), tetrakis(3-methylphenyl)-N,N,N′,N′-2,5-phenylenediamine (PDA),α-phenyl-4-N,N-diphenylaminostyrene (TPS), p-(diethylamino)benzaldehydediphenylhydrazone (DEH), triphenylamine (TPA),bis[4-(N,N-diethylamino)2-methylphenyl](4-methylphenyl)methane (MPMP),1-phenyl-3-[p-(diethylamino)styryl]5-[p-(diethylamino)phenyl]pyrazoline(PPR or DEASP), 1,2-trans-bis(9H-carbazol9-yl)-cyclobutane (DCZB),N,N,N′,N′-tetrakis(4-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine (TTB),fluorine compounds such as2,2′,7,7′-tetra(N,N-di-tolyl)amino9,9-spirobifluorene (spiro-TTB),N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)9,9-spirobifluorene(spiro-NPB) and9,9-bis(4-(N,N-bis-biphenyl-4-yl-amino)phenyl-9Hfluorene, benzidinecompounds such as N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidineand porphyrin compounds such as copper phthalocyanines. In addition,polymeric hole-injection materials can be used such aspoly(N-vinylcarbazole) (PVK), polythiophenes, polypyrrole, polyaniline,self-doping polymers, such as, for example, sulfonatedpoly(thiophene-3-[2[(2-methoxyethoxy)ethoxy]-2,5-diyl) (Plexcore® OCConducting Inks commercially available from Plextronics), and copolymerssuch as poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) alsocalled PEDOT/PSS. Preferred examples of a material of the hole injectinglayer are a porphyrin compound, an aromatic tertiary amine compound, ora styrylamine compound. Particularly preferable examples include anaromatic tertiary amine compound such as hexacyanohexaazatriphenylene(HAT).

In a preferred embodiment it is possible to use metal carbene complexesas hole transport materials. Suitable carbene complexes are, forexample, carbene complexes as described in WO2005/019373A2,WO2006/056418 A2, WO2005/113704, WO2007/115970, WO2007/115981,WO2008/000727 and PCT/EP2014/055520. One example of a suitable carbenecomplex is Ir(DPBIC)₃ with the formula:

Another example of a suitable carbene complex is Ir(ABIC)₃ with theformula:

The hole-transporting layer may also be electronically doped in order toimprove the transport properties of the materials used, in order firstlyto make the layer thicknesses more generous (avoidance of pinholes/shortcircuits) and in order secondly to minimize the operating voltage of thedevice. Electronic doping is known to those skilled in the art and isdisclosed, for example, in W. Gao, A. Kahn, J. Appl. Phys., Vol. 94,2003, 359 (p-doped organic layers); A. G. Werner, F. Li, K. Harada, M.Pfeiffer, T. Fritz, K. Leo, Appl. Phys. Lett., Vol. 82, No. 25, 2003,4495 and Pfeiffer et al., Organic Electronics 2003, 4, 89-103 and K.Walzer, B. Maennig, M. Pfeiffer, K. Leo, Chem. Soc. Rev. 2007, 107,1233. For example it is possible to use mixtures in thehole-transporting layer, in particular mixtures which lead to electricalp-doping of the hole-transporting layer. p-Doping is achieved by theaddition of oxidizing materials. These mixtures may, for example, be thefollowing mixtures: mixtures of the abovementioned hole transportmaterials with at least one metal oxide, for example MoO₂, MoO₃, WO_(x),ReO₃ and/or V₂O₅, preferably MoO₃ and/or ReO₃, more preferably MoO₃, ormixtures comprising the aforementioned hole transport materials and oneor more compounds selected from 7,7,8,8-tetracyanoquinodimethane (TCNQ),2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F₄-TCNQ),2,5-bis(2-hydroxyethoxy)-7,7,8,8-tetracyanoquinodimethane,bis(tetra-n-butylammonium)tetracyanodiphenoquinodimethane,2,5-dimethyl-7,7,8,8-tetracyanoquinodimethane, tetracyanoethylene,11,11,12,12-tetracyanonaphtho2,6-quinodimethane,2-fluoro-7,7,8,8-tetracyanoquino-dimethane,2,5-difluoro-7,7,8,8tetracyanoquinodimethane,dicyanomethylene-1,3,4,5,7,8-hexafluoro-6Hnaphthalen-2-ylidene)malononitrile(Fe-TNAP), Mo(tfd)₃ (from Kahn et al., J. Am. Chem. Soc. 2009, 131 (35),12530-12531), compounds as described in EP1988587, US2008265216,EP2180029, US20100102709, WO2010132236, EP2180029 and quinone compoundsas mentioned in EP2401254.

Preferred mixtures comprise the aforementioned carbene complexes, suchas, for example, the carbene complexes HTM-1 and HTM-2, and MoO₃ and/orReO₃, especially MoO₃. In a particularly preferred embodiment the holetransport layer comprises from 0.1 to 10 wt % of MoO₃ and 90 to 99.9 wt% carbene complex, especially of the carbene complex HTM-1 and HTM-2,wherein the total amount of the MoO₃ and the carbene complex is 100 wt%.

Exciton Blocking Layer (d):

Blocking layers may be used to reduce the number of charge carriers(electrons or holes) and/or excitons that leave the emissive layer. Anelectron/exciton blocking layer (d) may be disposed between the firstemitting layer (e) and the hole transport layer (c), to block electronsfrom emitting layer (e) in the direction of hole transport layer (c).Blocking layers may also be used to block excitons from diffusing out ofthe emissive layer. Suitable metal complexes for use as electron/excitonblocker material are, for example, carbene complexes as described inWO2005/019373A2, WO2006/056418A2, WO2005/113704, WO2007/115970,WO2007/115981, WO2008/000727 and PCT/EP2014/055520. Explicit referenceis made here to the disclosure of the WO applications cited, and thesedisclosures shall be considered to be incorporated into the content ofthe present application. Examples of suitable carbene complexes arecompounds HTM-1 and HTM-2.

Emitting Layer (e)

The light-emitting layer (e) comprises at least one emitter material. Inprinciple, it may be a fluorescence or phosphorescence emitter, suitableemitter materials being known to those skilled in the art. The at leastone emitter material is preferably a phosphorescence emitter. Thephosphorescence emitter compounds used with preference are based onmetal complexes, and especially the complexes of the metals Ru, Rh, Ir,Pd and Pt, in particular the complexes of Ir, have gained significance.The compounds of the formula I can be used as the matrix in thelight-emitting layer.

Suitable metal complexes for use in the inventive OLEDs, preferably asemitter material, are described, for example, in documents WO 02/60910A1, US 2001/0015432 A1, US 2001/0019782 A1, US 2002/0055014 A1, US2002/0024293 A1, US 2002/0048689 A1, EP 1 191 612 A2, EP 1 191 613 A2,EP 1 211 257 A2, US 2002/0094453 A1, WO 02/02714 A2, WO 00/70655 A2, WO01/41512 A1, WO 02/15645 A1, WO 2005/019373 A2, WO 2005/113704 A2, WO2006/115301 A1, WO 2006/067074 A1, WO 2006/056418, WO 2006121811 A1, WO2007095118 A2, WO 2007/115970, WO 2007/115981, WO 2008/000727,WO2010129323, WO2010056669, WO10086089, US2011/0057559, WO2011/106344,US2011/0233528, WO2012/048266 and WO2012/172482.

Further suitable metal complexes are the commercially available metalcomplexes tris(2-phenylpyridine)iridium(III), iridium(III)tris(2-(4-tolyl)pyridinato-N,C^(2′)),bis(2-phenylpyridine)(acetylacetonato)iridium(III), iridium(III)tris(1-phenylisoquinoline), iridium(III)bis(2,2′-benzothienyl)pyridinato-N,C^(3′))(acetylacetonate),tris(2-phenylquinoline)iridium(III), iridium(III)bis(2-(4,6-difluorophenyl)pyridinato-N,C²)picolinate, iridium(III)bis(1-phenylisoquinoline)(acetylacetonate),bis(2-phenylquinoline)(acetylacetonato)iridium(III), iridium(III)bis(di-benzo[f,h]quinoxaline)(acetylacetonate), iridium(III)bis(2-methyldibenzo[f,h]quinoxaline)acetylacetonate) andtris(3-methyl-1-phenyl-4-trimethylacetyl-5-pyrazolino)terbium(III),bis[1-(9,9-dimethyl-9H-fluoren-2-yl)isoquinoline](acetylacetonato)iridium(III),bis(2-phenylbenzothiazolato)(acetylacetonato)iridium(III),bis(2-(9,9-dihexylfluorenyl)-1-pyridine)(acetylacetonato)iridium(III),bis(2-benzo[b]thiophen-2-yl-pyridine)(acetylacetonato)iridium(III).

In addition, the following commercially available materials aresuitable: tris(dibenzoylacetonato)mono(phenanthroline)europium(III),tris(dibenzoylmethane)-mono(phenanthroline)europium(III),tris(dibenzoylmethane)mono(5-aminophenanthroline)-europium(III),tris(di-2-naphthoylmethane)mono(phenanthroline)europium(III),tris(4-bromobenzoylmethane)mono(phenanthroline)europium(III),tris(di(biphenyl)methane)-mono(phenanthroline)europium(III),tris(dibenzoylmethane)mono(4,7-diphenyl-phenanthroline)europium(III),tris(dibenzoylmethane)mono(4,7-di-methyl-phenanthroline)europium(III),tris(dibenzoylmethane)mono(4,7-dimethylphenanthrolinedisulfonicacid)europium(III) disodium salt,tris[di(4-(2-(2-ethoxyethoxy)ethoxy)benzoylmethane)]mono-(phenanthroline)europium(III)andtris[di[4-(2-(2-ethoxyethoxy)ethoxy)benzoylmethane)]mono(5-aminophenanthroline)europium(III),osmium(II)bis(3-(trifluoromethyl)-5-(4-tert-butylpyridyl)-1,2,4-triazolato)diphenylmethylphosphine,osmium(II)bis(3-(trifluoromethyl)-5-(2-pyridyl)-1,2,4-triazole)dimethylphenylphosphine,osmium(II)bis(3-(trifluoromethyl)-5-(4-tert-butylpyridyl)-1,2,4-triazolato)dimethylphenylphosphine,osmium(II)bis(3-(trifluoromethyl)-5-(2-pyridyl)-pyrazolato)dimethylphenylphosphine,tris[4,4′-di-tert-butyl(2,2′)-bipyridine]ruthenium(III), osmium(II)bis(2-(9,9-dibutylfluorenyl)-1-isoquinoline(acetylacetonate).

Preferred phosphorescence emitters are carbene complexes.

Suitable phosphorescent blue emitters are specified in the followingpublications: WO2006/056418A2, WO2005/113704, WO2007/115970,WO2007/115981, WO2008/000727, WO2009050281, WO2009050290, WO2011051404,US2011/057559 WO2011/073149, WO2012/121936A2, US2012/0305894A1,WO2012/170571, WO2012/170461, WO2012/170463, WO2006/121811,WO2007/095118, WO2008/156879, WO2008/156879, WO2010/068876,US2011/0057559, WO2011/106344, US2011/0233528, WO2012/048266,WO2012/172482, PCT/EP2014/064054 and PCT/EP2014/066272.

Preferably, the light emitting layer (e) comprises at least one carbenecomplex as phosphorescence emitter. Suitable carbene complexes are, forexample, compounds of the formula

which are described in WO 2005/019373 A2, wherein the symbols have thefollowing meanings:

M is a metal atom selected from the group consisting of Co, Rh, Ir, Nb,Pd, Pt, Fe, Ru, Os, Cr, Mo, W, Mn, Tc, Re, Cu, Ag and Au in anyoxidation state possible for the respective metal atom; carbene is acarbene ligand which may be uncharged or monoanionic and monodentate,bidentate or tridentate, with the carbene ligand also being able to be abiscarbene or triscarbene ligand;

L is a monoanionic or dianionic ligand, which may be monodentate orbidentate;

K is an uncharged monodentate or bidentate ligand, preferably selectedfrom the group consisting of phosphines; phosphonates and derivativesthereof, arsenates and derivatives thereof; phosphites; CO; pyridines;nitriles and conjugated dienes which form a π complex with M¹;

n1 is the number of carbene ligands, where n1 is at least 1 and whenn1>1 the carbene ligands in the complex of the formula I can beidentical or different;

m1 is the number of ligands L, where m1 can be 0 or ≥1 and when m1>1 theligands L can be identical or different;

o is the number of ligands K, where o can be 0 or ≥1 and when o>1 theligands K can be identical or different;

where the sum n1+m1+o is dependent on the oxidation state andcoordination number of the metal atom and on the denticity of theligands carbene, L and K and also on the charge on the ligands, carbeneand L, with the proviso that n1 is at least 1.

More preferred are metal-carbene complexes of the general formula

which are described in WO2011/073149, where M is Ir, or Pt,

n1 is an integer selected from 1, 2 and 3,

Y is NR^(51′), O, S or C(R^(25′))₂,

A^(2′), A^(3′), A^(4′), and A^(5′) are each independently N or C, where2 A′=nitrogen atoms and at least one carbon atom is present between twonitrogen atoms in the ring,

R^(51′) is a linear or branched alkyl radical optionally interrupted byat least one heteroatom, optionally bearing at least one functionalgroup and having 1 to 20 carbon atoms, cycloalkyl radical optionallyinterrupted by at least one heteroatom, optionally bearing at least onefunctional group and having 3 to 20 carbon atoms, substituted orunsubstituted aryl radical optionally interrupted by at least oneheteroatom, optionally bearing at least one functional group and having6 to 30 carbon atoms, substituted or unsubstituted heteroaryl radicaloptionally interrupted by at least one heteroatom, optionally bearing atleast one functional group and having a total of 5 to 18 carbon atomsand/or heteroatoms,

R^(52′), R^(53′), R^(54′) and R^(55′) are each, if A^(2′), A^(3′),A^(4′) and/or A^(5′) is N, a free electron pair, or, if A^(2′), A^(3′),A^(4′) and/or A^(5′) is C, each independently hydrogen, linear orbranched alkyl radical optionally interrupted by at least oneheteroatom, optionally bearing at least one functional group and having1 to 20 carbon atoms, cycloalkyl radical optionally interrupted by atleast one heteroatom, optionally bearing at least one functional groupand having 3 to 20 carbon atoms, substituted or unsubstituted arylradical optionally interrupted by at least one heteroatom, optionallybearing at least one functional group and having 6 to 30 carbon atoms,substituted or unsubstituted heteroaryl radical optionally interruptedby at least one heteroatom, optionally bearing at least one functionalgroup and having a total of 5 to 18 carbon atoms and/or heteroatoms,group with donor or acceptor action, or

R^(53′) and R^(54′) together with A^(3′) and A^(4′) form an optionallysubstituted, unsaturated ring optionally interrupted by at least onefurther heteroatom and having a total of 5 to 18 carbon atoms and/orheteroatoms,

R^(56′), R^(57′), R^(58′) and R^(59′) are each independently hydrogen,linear or branched alkyl radical optionally interrupted by at least oneheteroatom, optionally bearing at least one functional group and having1 to 20 carbon atoms, cycloalkyl radical optionally interrupted by atleast one heteroatom, optionally bearing at least one functional groupand having 3 to 20 carbon atoms, cycloheteroalkyl radical optionallyinterrupted by at least one heteroatom, optionally bearing at least onefunctional group and having 3 to 20 carbon atoms, substituted orunsubstituted aryl radical optionally interrupted by at least oneheteroatom, optionally bearing at least one functional group and having6 to 30 carbon atoms, substituted or unsubstituted heteroaryl radicaloptionally interrupted by at least one heteroatom, optionally bearing atleast one functional group and having a total of 5 to 18 carbon atomsand/or heteroatoms, group with donor or acceptor action, or

R^(56′) and R_(57′), R^(57′) and R^(58′) or R^(58′) and R^(59′),together with the carbon atoms to which they are bonded, form asaturated, unsaturated or aromatic, optionally substituted ringoptionally interrupted by at least one heteroatom and having a total of5 to 18 carbon atoms and/or heteroatoms, and/or

if A^(5′) is C, R^(55′) and R^(56′) together form a saturated orunsaturated, linear or branched bridge optionally comprisingheteroatoms, an aromatic unit, heteroaromatic unit and/or functionalgroups and having a total of 1 to 30 carbon atoms and/or heteroatoms, towhich is optionally fused a substituted or unsubstituted, five- toeight-membered ring comprising carbon atoms and/or heteroatoms,

R^(25′) is independently a linear or branched alkyl radical optionallyinterrupted by at least one heteroatom, optionally bearing at least onefunctional group and having 1 to 20 carbon atoms, cycloalkyl radicaloptionally interrupted by at least one heteroatom, optionally bearing atleast one functional group and having 3 to 20 carbon atoms, substitutedor unsubstituted aryl radical optionally interrupted by at least oneheteroatom, optionally bearing at least one functional group and having6 to 30 carbon atoms, substituted or unsubstituted heteroaryl radicaloptionally interrupted by at least one heteroatom, optionally bearing atleast one functional group and having a total of 5 to 18 carbon atomsand/or heteroatoms,

K is an uncharged mono- or bidentate ligand,

L is a mono- or dianionic ligand, preferably monoanionic ligand, whichmay be mono- or bidentate,

m1 is 0, 1 or 2, where, when m1 is 2, the K ligands may be the same ordifferent,

o1 is 0, 1 or 2, where, when o1 is 2, the L ligands may be the same ordifferent

The compound of formula XIV is preferably a compound of the formula:

Further suitable non-carbene emitter materials are mentioned below:

The compound of formula XIV is more preferably a compound (BE-1),(BE-2), (BE-7), (BE-12), (BE-16), (BE-64), or (BE-70). The mostpreferred phosphorescent blue emitters are compounds (BE-1) and (BE-12).

The homoleptic metal-carbene complexes may be present in the form offacial or meridional isomers or mixtures thereof, preference being givento the facial isomers.

Suitable carbene complexes of formula (XIV) and their preparationprocess are, for example, described in WO2011/073149.

The compounds of the present invention can also be used as host forphosphorescent green emitters. Suitable phosphorescent green emittersare, for example, specified in the following publications: WO2006014599,WO20080220265, WO2009073245, WO2010027583, WO2010028151, US20110227049,WO2011090535, WO2012/08881, WO20100056669, WO20100118029, WO20100244004,WO2011109042, WO2012166608, US20120292600, EP2551933A1; U.S. Pat. No.6,687,266, US20070190359, US20070190359, US20060008670; WO2006098460,US20110210316, WO2012053627; U.S. Pat. No. 6,921,915, US20090039776;JP2007123392 and European patent application no. 14180422.9.

Examples of suitable phosphorescent green emitters are shown below:

Host (Matrix) Materials

The light-emitting layer may comprise further components in addition tothe emitter material. For example, a fluorescent dye may be present inthe light-emitting layer in order to alter the emission color of theemitter material. In addition—in a preferred embodiment—a matrixmaterial can be used. This matrix material may be a polymer, for examplepoly(N-vinylcarbazole) or polysilane. The matrix material may, however,be a small molecule, for example 4,4′-N,N′-dicarbazolebiphenyl (CDP=CBP)or tertiary aromatic amines, for example TCTA.

In a preferred embodiment, the light-emitting layer is formed of atleast one emitter material and of at least one of the matrixmaterials—in one embodiment at least one compound of the formula I.Suitable emitter materials and matrix materials are mentioned in thespecification. In one embodiment, the light-emitting layer comprises atleast one emitter material and at least to matrix materials, wherein oneof the matrix materials is a first host material and the other is asecond host material. The matrix materials mentioned in thespecification are suitable as first and second host materials.

In another preferred embodiment of the present invention, at least onecompound of the formula I is used as host material. Examples ofpreferred compounds of formula I useful as host material are shownabove.

In a more preferred embodiment, the light-emitting layer is formed from2 to 40% by weight, preferably 5 to 35% by weight, of at least one ofthe aforementioned emitter materials and 60 to 98% by weight, preferably75 to 95% by weight, of at least one of the matrix materials mentionedin the specification—in one embodiment at least one compound of theformula I—where the sum total of the emitter material and of the matrixmaterial adds up to 100% by weight.

In a particularly preferred embodiment, the light-emitting layercomprises a compound of formula I and two carbene complexes, preferablyBE-1 and HTM-1, or HTM-2. In said embodiment, the light-emitting layeris formed from 2 to 40% by weight, preferably 5 to 35% by weight, ofBE-1 and 60 to 98% by weight, preferably 65 to 95% by weight, of acompound of the formula I and and HTM-1, or HTM-2, where the sum totalof the carbon complexes and of the compound of formula I adds up to 100%by weight.

Suitable metal complexes for use as matrix material in OLEDs, preferablytogether with the compounds of the formula I, are, for example, alsocarbene complexes as described in WO 2005/019373 A2, WO 2006/056418 A2,WO 2005/113704, WO 2007/115970, WO 2007/115981 and WO 2008/000727.

Further suitable host materials, which may be small molecules or(co)polymers of the small molecules mentioned, are specified in thefollowing publications: WO2007108459 (H-1 to H-37), preferably H-20 toH-22 and H-32 to H-37, most preferably H-20, H-32, H-36, H-37,WO2008035571 A1 (Host 1 to Host 6), JP2010135467 (compounds 1 to 46 andHost-1 to Host-39 and Host-43), WO2009008100 compounds No. 1 to No. 67,preferably No. 3, No. 4, No. 7 to No. 12, No. 55, No. 59, No. 63 to No.67, more preferably No. 4, No. 8 to No. 12, No. 55, No. 59, No. 64, No.65, and No. 67, WO2009008099 compounds No. 1 to No. 110, WO2008140114compounds 1-1 to 1-50, WO2008090912 compounds OC-7 to OC-36 and thepolymers of Mo-42 to Mo-51, JP2008084913 H-1 to H-70, WO2007077810compounds 1 to 44, preferably 1, 2, 4-6, 8, 19-22, 26, 28-30, 32, 36,39-44, WO201001830 the polymers of monomers 1-1 to 1-9, preferably of1-3, 1-7, and 1-9, WO2008029729 the (polymers of) compounds 1-1 to 1-36,WO20100443342 HS-1 to HS-101 and BH-1 to BH-17, preferably BH-1 toBH-17, JP2009182298 the (co)polymers based on the monomers 1 to 75,JP2009170764, JP2009135183 the (co)polymers based on the monomers 1-14,WO2009063757 preferably the (co)polymers based on the monomers 1-1 to1-26, WO2008146838 the compounds a-1 to a-43 and 1-1 to 1-46,JP2008207520 the (co)polymers based on the monomers 1-1 to 1-26,JP2008066569 the (co)polymers based on the monomers 1-1 to 1-16,WO2008029652 the (co)polymers based on the monomers 1-1 to 1-52,WO2007114244 the (co)polymers based on the monomers 1-1 to 1-18,JP2010040830 the compounds HA-1 to HA-20, HB-1 to HB-16, HC-1 to HC-23and the (co)polymers based on the monomers HD-1 to HD-12, JP2009021336,WO2010090077 the compounds 1 to 55, WO2010079678 the compounds H1 toH42, WO2010067746, WO2010044342 the compounds HS-1 to HS-101 and Poly-1to Poly-4, JP2010114180 the compounds PH-1 to PH-36, US2009284138 thecompounds 1 to 111 and H1 to H71, WO2008072596 the compounds 1 to 45,JP2010021336 the compounds H-1 to H-38, preferably H-1, WO2010004877 thecompounds H-1 to H-60, JP2009267255 the compounds 1-1 to 1-105,WO2009104488 the compounds 1-1 to 1-38, WO2009086028, US2009153034,US2009134784, WO2009084413 the compounds 2-1 to 2-56, JP2009114369 thecompounds 2-1 to 2-40, JP2009114370 the compounds 1 to 67, WO2009060742the compounds 2-1 to 2-56, WO2009060757 the compounds 1-1 to 1-76,WO2009060780 the compounds 1-1 to 1-70, WO2009060779 the compounds 1-1to 1-42, WO2008156105 the compounds 1 to 54, JP2009059767 the compounds1 to 20, JP2008074939 the compounds 1 to 256, JP2008021687 the compounds1 to 50, WO2007119816 the compounds 1 to 37, WO2010087222 the compoundsH-1 to H-31, WO2010095564 the compounds HOST-1 to HOST-61, WO2007108362,WO2009003898, WO2009003919, WO2010040777, US2007224446, WO06128800,WO2012014621, WO2012105310, WO2012/130709 and European patentapplications EP12175635.7, EP12185230.5 and EP12191408.9 (in particularpage 25 to 29 of EP12191408.9).

The above-mentioned small molecules are more preferred than theabove-mentioned (co)polymers of the small molecules.

Further suitable host materials, are described in WO2011137072 (forexample

best results are achieved if said compounds are combined with

WO2012048266 (for example,

WO2012162325 (for example,

and EP2551932 (for example,

In a particularly preferred embodiment, one or more compounds of thegeneral formula (XV) specified hereinafter are used as host material.

wherein

X is NR, S, O or PR;

R is aryl, heteroaryl, alkyl, cycloalkyl, or heterocycloalkyl;

A²⁰⁰ is —NR²⁰⁶R²⁰⁷, —P(O)R²⁰⁸R²⁰⁹, —PR²¹⁰R²¹¹, —S(O)₂R²¹², —S(O)R²¹³,—SR²¹⁴, or —OR²¹⁵;

R²²¹, R²²² and R²²³ are independently of each other aryl, heteroaryl,alkyl, cycloalkyl, or heterocycloalkyl, wherein at least on of thegroups R²²¹, R²²², or R²²³ is aryl, or heteroaryl;

R²²⁴ and R²²⁵ are independently of each other alkyl, cycloalkyl,heterocycloalkyl, aryl, heteroaryl, a group A²⁰⁰, or a group havingdonor, or acceptor characteristics;

n2 and m2 are independently of each other 0, 1, 2, or 3;

R²⁰⁶ and R²⁰⁷ form together with the nitrogen atom a cyclic residuehaving 3 to 10 ring atoms, which can be unsubstituted, or which can besubstituted with one, or more substituents selected from alkyl,cycloalkyl, heterocycloalkyl, aryl, heteroaryl and a group having donor,or acceptor characteristics; and/or which can be annulated with one, ormore further cyclic residues having 3 to 10 ring atoms, wherein theannulated residues can be unsubstituted, or can be substituted with one,or more substituents selected from alkyl, cycloalkyl, heterocycloalkyl,aryl, heteroaryl and a group having donor, or acceptor characteristics;and

R²⁰⁸, R²⁰⁹, R²¹⁰, R²¹¹, R²¹², R²¹³, R²¹⁴ und R²¹⁵ are independently ofeach other aryl, heteroaryl, alkyl, cycloalkyl, or heterocycloalkyl.Compounds of formula XV, such as, for example,

are described in WO2010079051 (in particular pages on 19 to 26 and intables on pages 27 to 34, pages 35 to 37 and pages 42 to 43).

Additional host materials on basis of dibenzofurane are, for example,described in US2009066226, EP1885818B1, EP1970976, EP1998388, EP2034538and European patent application no. 14160197.1. Examples of particularlypreferred host materials are shown below:

In the above-mentioned compounds T is O, or S, preferably O. If T occursmore than one time in a molecule, all groups T have the same meaning. T¹is O, or S, preferably O. T¹ and T² are independently of each other

wherein T¹⁰ is a C₁-C₂₅alkyl group.

Compounds

are most preferred.

TADF Material

In a further embodiment of the present invention, the compounds offormula I are employed as TADF material in the light-emitting layer ofan OLED. The compounds of formula I are used as TADF emitter or as TADFhost materials in combination with fluorescent emitters.

Suitable host materials in combination with the compounds of formula Ias emitter material as well as suitable fluorescent emitter material incombination with the compounds of formula I as TADF host material areknown by a person skilled in the art.

Hole/Exciton Blocking Layer (f):

Blocking layers may be used to reduce the number of charge carriers(electrons or holes) and/or excitons that leave the emissive layer. Thehole blocking layer may be disposed between the emitting layer (e) andelectron transport layer (g), to block holes from leaving layer (e) inthe direction of electron transport layer (g). Blocking layers may alsobe used to block excitons from diffusing out of the emissive layer.

Additional hole blocker materials typically used in OLEDs are2,6-bis(N-carbazolyl)pyridine (mCPy),2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (bathocuproin, (BCP)),bis(2-methyl-8-quinolinato)-4-phenylphenylato)aluminum(III) (BAlq),phenothiazine S,S-dioxide derivates and1,3,5-tris(N-phenyl-2-benzylimidazolyl)benzene) (TPBI), TPBI also beingsuitable as electron-transport material. Further suitable hole blockersand/or electron conductor materials are2,2′,2″-(1,3,5-benzenetriyl)tris(1-phenyl-1-H-benzimidazole),2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole,8-hydroxyquinolinolatolithium,4-(naphthalen-1-yl)-3,5-diphenyl-4H-1,2,4-triazole,1,3-bis[2-(2,2′-bipyridin-6-yl)-1,3,4-oxadiazo-5-yl]benzene,4,7-diphenyl-1,10-phenanthroline,3-(4-biphenylyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole,6,6′-bis[5-(biphenyl-4-yl)-1,3,4-oxadiazo-2-yl]-2,2′-bipyridyl,2-phenyl-9,10-di(naphthalene-2-yl)anthracene,2,7-bis[2-(2,2′-bipyridin-6-yl)-1,3,4-oxadiazo-5-yl]-9,9-dimethylfluorene,1,3-bis[2-(4-tert-butylphenyl)-1,3,4-oxadiazo-5-yl]benzene,2-(naphthalene-2-yl)-4,7-diphenyl-1,10-phenanthroline,tris(2,4,6-trimethyl-3-(pyridin-3-yl)phenyl)borane,2,9-bis(naphthalene-2-yl)-4,7-diphenyl-1,10-phenanthroline,1-methyl-2-(4-(naphthalene-2-yl)phenyl)-1H-imidazo[4,5-f][1,10]-phenanthroline.In a further embodiment, it is possible to use compounds which comprisearomatic or heteroaromatic rings joined via groups comprising carbonylgroups, as disclosed in WO2006/100298, disilyl compounds selected fromthe group consisting of disilylcarbazoles, disilylbenzofurans,disilylbenzothiophenes, disilylbenzophospholes, disilylbenzothiopheneS-oxides and disilylbenzothiophene S,S-dioxides, as specified, forexample, in PCT applications WO2009/003919 and WO2009003898 and disilylcompounds as disclosed in WO2008/034758, as a blocking layer forholes/excitons (f).

In another preferred embodiment compounds (SH-1), (SH-2), (SH-3), SH-4,SH-5, SH-6, (SH-7), (SH-8), (SH-9), (SH-10) and (SH-11) may be used ashole/exciton blocking materials.

Electron Transport Layer (g):

Electron transport layer may include a material capable of transportingelectrons. Electron transport layer may be intrinsic (undoped), ordoped. Doping may be used to enhance conductivity. Suitableelectron-transporting materials for layer (g) of the inventive OLEDscomprise metals chelated with oxinoid compounds, such astris(8-hydroxyquinolato)aluminum (Alq₃), compounds based onphenanthroline such as 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline(DDPA=BCP), 4,7-diphenyl-1,10-phenanthroline (Bphen),2,4,7,9-tetraphenyl-1,10-phenanthroline,4,7-diphenyl-1,10-phenanthroline (DPA) or phenanthroline derivativesdisclosed in EP1786050, in EP1970371, or in EP1097981, and azolecompounds such as 2-(4-biphenylyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole(PBD) and 3-(4-biphenylyl)-4phenyl-5-(4-t-butylphenyl)-1,2,4-triazole(TAZ).

It is likewise possible to use mixtures of at least two materials in theelectron-transporting layer, in which case at least one material iselectron-conducting. Preferably, in such mixed electron-transportlayers, at least one phenanthroline compound is used, preferably BCP, orat least one pyridine compound according to the formula (XVI) below,preferably a compound of the formula (XVIa) below. More preferably, inmixed electron-transport layers, in addition to at least onephenanthroline compound, alkaline earth metal or alkali metalhydroxyquinolate complexes, for example Liq, are used. Suitable alkalineearth metal or alkali metal hydroxyquinolate complexes are specifiedbelow (formula XVII). Reference is made to WO2011/157779.

The electron-transport layer may also be electronically doped in orderto improve the transport properties of the materials used, in orderfirstly to make the layer thicknesses more generous (avoidance ofpinholes/short circuits) and in order secondly to minimize the operatingvoltage of the device. Electronic doping is known to those skilled inthe art and is disclosed, for example, in W. Gao, A. Kahn, J. Appl.Phys., Vol. 94, No. 1, 1 Jul. 2003 (p-doped organic layers); A. G.Werner, F. Li, K. Harada, M. Pfeiffer, T. Fritz, K. Leo, Appl. Phys.Lett., Vol. 82, No. 25, 23 Jun. 2003 and Pfeiffer et al., OrganicElectronics 2003, 4, 89-103 and K. Walzer, B. Maennig, M. Pfeiffer, K.Leo, Chem. Soc. Rev. 2007, 107, 1233. For example, it is possible to usemixtures which lead to electrical n-doping of the electron-transportlayer. n-Doping is achieved by the addition of reducing materials. Thesemixtures may, for example, be mixtures of the abovementioned electrontransport materials with alkali/alkaline earth metals or alkali/alkalineearth metal salts, for example Li, Cs, Ca, Sr, Cs₂CO₃, with alkali metalcomplexes, for example 8-hydroxyquinolatolithium (Liq), and with Y, Ce,Sm, Gd, Tb, Er, Tm, Yb, Li₃N, Rb₂CO₃, dipotassium phthalate, W(hpp)₄from EP1786050, or with compounds described in EP1837926B1, EP1837927,EP2246862 and WO2010132236.

In a preferred embodiment, the electron-transport layer comprises atleast one compound of the general formula (XVII)

in which

R^(32′) and R^(33′) are each independently F, C₁-C₈-alkyl, orC₆-C₁₄-aryl, which is optionally substituted by one or more C₁-C₈-alkylgroups, or

two R^(32′) and/or R^(33′) substituents together form a fused benzenering which is optionally substituted by one or more C₁-C₈-alkyl groups;

a and b are each independently 0, or 1, 2 or 3,

M¹ is an alkaline metal atom or alkaline earth metal atom,

p is 1 when M¹ is an alkali metal atom, p is 2 when M¹ is an earthalkali metal atom.

A very particularly preferred compound of the formula (XVII) is

which may be present as a single species, or in other forms such asLi_(g)Q_(g) in which g is an integer, for example Li₆Q₆. Q is an8-hydroxyquinolate ligand or an 8-hydroxyquinolate derivative.

In a further preferred embodiment, the electron-transport layercomprises at least one compound of the formula (XVI),

in which

R^(34″), R_(35″), R^(36″), R^(37″), R^(34′), R^(35′), R^(36′) andR^(37′) are each independently H, C₁-C₁₈-alkyl, C₁-C₁₈-alkyl which issubstituted by E′ and/or interrupted by D′, C₆-C₂₄-aryl, C₆-C₂₄-arylwhich is substituted by G′, C₂-C₂₀-heteroaryl or C₂-C₂₀-heteroaryl whichis substituted by G′,

Q is an arylene or heteroarylene group, each of which is optionallysubstituted by G′;

D′ is —CO—; —COO—; —S—; —SO—; —SO₂—; —O—; —NR^(40′)—;—SiR^(45′)R^(46′)—; —POR^(47′)—; —CR^(38′)═CR^(39′)—; or —C≡C—;

E′ is —OR^(44′); —SR^(44′); —NR^(40′)R^(41′); —COR^(43′); —COOR^(42′);—CONR^(40′)R^(41′); —CN; or F;

G′ is E′, C₁-C₁₈-alkyl, C₁-C₁₈-alkyl which is interrupted by D′,C₁-C₁₈-perfluoroalkyl, C₁-C₁₈-alkoxy, or C₁-C₁₈-alkoxy which issubstituted by E′ and/or interrupted by D′, in which

R^(38′) and R^(39′) are each independently H, C₆-C₁₈-aryl; C₆-C₁₈-arylwhich is substituted by C₁-C₁₈-alkyl or C₁-C₁₈-alkoxy; C₁-C₁₈-alkyl; orC₁-C₁₈-alkyl which is interrupted by —O—;

R^(40′) and R^(41′) are each independently C₆-C₁₈-aryl; C₆-C₁₈-arylwhich is substituted by C₁-C₁₈-alkyl or C₁-C₁₈-alkoxy; C₁-C₁₈-alkyl; orC₁-C₁₈-alkyl which is interrupted by —O—; or

R^(40′) and R^(41′) together form a 6-membered ring;

R^(42′) and R^(43′) are each independently C₆-C₁₈-aryl; C₆-C₁₈-arylwhich is substituted by C₁-C₁₈-alkyl or C₁-C₁₈-alkoxy; C₁-C₁₈-alkyl; orC₁-C₁₈-alkyl which is interrupted by —O—,

R^(44′) is C₆-C₁₈-aryl; C₆-C₁₈-aryl which is substituted by C₁-C₁₈-alkylor C₁-C₁₈-alkoxy; C₁-C₁₈-alkyl; or C₁-C₁₈-alkyl which is interrupted by—O—,

R_(45′) and R^(46′) are each independently C₁-C₁₈-alkyl, C₆-C₁₈-aryl orC₆-C₁₈-aryl which is substituted by C₁-C₁₈-alkyl,

R^(47′) is C₁-C₁₈-alkyl, C₆-C₁₈-aryl or C₆-C₁₈-aryl which is substitutedby C₁-C₁₈-alkyl.

Preferred compounds of the formula (XVI) are compounds of the formula(XVIa)

in which Q is:

R^(48′) is H or C₁-C₁₈-alkyl and

R^(48″) is H, C₁-C₁₈-alkyl or

Particular preference is given to a compound of the formula

In a further, very particularly preferred embodiment, theelectron-transport layer comprises a compound Liq and a compound ETM-2.

In a preferred embodiment, the electron-transport layer comprises atleast one compound of the formula (XVII) in an amount of 99 to 1% byweight, preferably 75 to 25% by weight, more preferably about 50% byweight, and at least one compound of the formula (XVI) in an amount of 1to 99% by weight, preferably 25 to 75% by weight, more preferably about50% by weight, where the amount of the compounds of the formulae (XVII)and the amount of the compounds of the formulae (XVI) adds up to a totalof 100% by weight

The preparation of the compounds of the formula (XVI) is described in J.Kido et al., Chem. Commun. (2008) 5821-5823, J. Kido et al., Chem.Mater. 20 (2008) 5951-5953 and JP2008/127326, or the compounds can beprepared analogously to the processes disclosed in the aforementioneddocuments.

It is likewise possible to use mixtures of alkali metal hydroxyquinolatecomplexes, preferably Liq, and dibenzofuran compounds in theelectron-transport layer. Reference is made to WO2011/157790.Dibenzofuran compounds A-1 to A-36 and B-1 to B-22 described inWO2011/157790 are preferred, wherein dibenzofuran compound

(A-10; =ETM-1) is most preferred.

In a preferred embodiment, the electron-transport layer comprises Liq inan amount of 99 to 1% by weight, preferably 75 to 25% by weight, morepreferably about 50% by weight, and at least one dibenzofuran compoundin an amount of 1 to 99% by weight, preferably 25 to 75% by weight, morepreferably about 50% by weight, where the amount of Liq and the amountof the dibenzofuran compound(s), especially ETM-1, adds up to a total of100% by weight

In a preferred embodiment, the electron-transport layer comprises atleast one phenanthroline derivative and/or pyridine derivative.

In a further preferred embodiment, the electron-transport layercomprises at least one phenanthroline derivative and/or pyridinederivative and at least one alkali metal hydroxyquinolate complex.

In a further preferred embodiment, the electron-transport layercomprises at least one of the dibenzofuran compounds A-1 to A-36 and B-1to B-22 described in WO2011/157790, especially ETM-1.

In a further preferred embodiment, the electron-transport layercomprises a compound described in WO2012/111462, WO2012/147397,WO2012014621, such as, for example, a compound of formula

US2012/0261654, such as, for example, a compound of formula

and WO2012/115034, such as for example, such as, for example, a compoundof formula

Electron Injection Layer (h):

The electron injection layer may be any layer that improves theinjection of electrons into an adjacent organic layer.Lithium-comprising organometallic compounds such as8-hydroxyquinolatolithium (Liq), CsF, NaF, KF, Cs₂CO₃ or LiF may beapplied between the electron transport layer (g) and the cathode (i) asan electron injection layer (h) in order to reduce the operatingvoltage.

Cathode (i):

The cathode (i) is an electrode which serves to introduce electrons ornegative charge carriers. The cathode may be any metal or nonmetal whichhas a lower work function than the anode. Suitable materials for thecathode are selected from the group consisting of alkali metals of group1, for example Li, Cs, alkaline earth metals of group 2, metals of group12 of the Periodic Table of the Elements, comprising the rare earthmetals and the lanthanides and actinides. In addition, metals such asaluminum, indium, calcium, barium, samarium and magnesium, andcombinations thereof, may be used.

In general, the different layers, if present, have the followingthicknesses:

anode (a): 500 to 5000 Å (ångström), preferably 1000 to 2000 Å;

hole injection layer (b): 50 to 1000 Å, preferably 200 to 800 Å,

hole-transport layer (c): 50 to 1000 Å, preferably 100 to 800 Å,

exciton blocking layer (d): 10 to 500 Å, preferably 50 to 100 Å,

light-emitting layer (e): 10 to 1000 Å, preferably 50 to 600 Å,

hole/exciton blocking layer (f): 10 to 500 Å, preferably 50 to 100 Å,

electron-transport layer (g): 50 to 1000 Å, preferably 200 to 800 Å,

electron injection layer (h): 10 to 500 Å, preferably 20 to 100 Å,

cathode (i): 200 to 10 000 Å, preferably 300 to 5000 Å.

The person skilled in the art is aware (for example on the basis ofelectrochemical studies) of how suitable materials have to be selected.Suitable materials for the individual layers are known to those skilledin the art and are disclosed, for example, in WO 00/70655.

In addition, it is possible that some of the layers used in theinventive OLED have been surface-treated in order to increase theefficiency of charge carrier transport. The selection of the materialsfor each of the layers mentioned is preferably determined by obtainingan OLED with a high efficiency and lifetime.

The inventive OLED can be produced by methods known to those skilled inthe art. In general, the inventive OLED is produced by successive vapordeposition of the individual layers onto a suitable substrate. Suitablesubstrates are, for example, glass, inorganic semiconductors or polymerfilms. For vapor deposition, it is possible to use customary techniques,such as thermal evaporation, chemical vapor deposition (CVD), physicalvapor deposition (PVD) and others. In an alternative process, theorganic layers of the OLED can be applied from solutions or dispersionsin suitable solvents, employing coating techniques known to thoseskilled in the art.

Use of the compounds of the formula I in at least one layer of the OLED,preferably in the light-emitting layer (preferably as a matrixmaterial), charge transport layer and/or in the charge/exciton blockinglayer makes it possible to obtain OLEDs with high efficiency and withlow use and operating voltage. Frequently, the OLEDs obtained by the useof the compounds of the formula I additionally have high lifetimes. Theefficiency of the OLEDs can additionally be improved by optimizing theother layers of the OLEDs. For example, high-efficiency cathodes such asCa or Ba, if appropriate in combination with an intermediate layer ofLiF, can be used. Moreover, additional layers may be present in theOLEDs in order to adjust the energy level of the different layers and tofacilitate electroluminescence.

The OLEDs may further comprise at least one second light-emitting layer.The overall emission of the OLEDs may be composed of the emission of theat least two light-emitting layers and may also comprise white light.

The OLEDs can be used in all apparatus in which electroluminescence isuseful. Suitable devices are preferably selected from stationary andmobile visual display units and illumination units. Stationary visualdisplay units are, for example, visual display units of computers,televisions, visual display units in printers, kitchen appliances andadvertising panels, illuminations and information panels. Mobile visualdisplay units are, for example, visual display units in cellphones,tablet PCs, laptops, digital cameras, MP3 players, vehicles anddestination displays on buses and trains. Further devices in which theinventive OLEDs can be used are, for example, keyboards; items ofclothing; furniture; wallpaper. In addition, the present inventionrelates to a device selected from the group consisting of stationaryvisual display units such as visual display units of computers,televisions, visual display units in printers, kitchen appliances andadvertising panels, illuminations, information panels, and mobile visualdisplay units such as visual display units in cellphones, tablet PCs,laptops, digital cameras, MP3 players, vehicles and destination displayson buses and trains; illumination units; keyboards; items of clothing;furniture; wallpaper, comprising at least one inventive organiclight-emitting diode or at least one inventive light-emitting layer.

The following examples are included for illustrative purposes only anddo not limit the scope of the claims. Unless otherwise stated, all partsand percentages are by weight.

EXAMPLES I Preparation Examples Example 1

2.92 g (20.0 mmol) of 1,3-dicyano-5-fluoro-benzene, 4.14 g (20.0 mmol)of 6H-benzimidazolo[1,2-a]benzimidazole and 4.25 g (20.0 mmol) oftripotassium phosphate in 50 ml of DMF are stirred for 2 h at 120° C.The reaction mixture is cooled at room temperature and added water, thenthe precipitate is filtered off. Gradient column chromatography onsilica gel with dichloromethane/ethyl acetate (dichloromethane 100%,9/1, 4/1) gives the product. Yield 6.13 g (92%).

¹H NMR (400 MHz, CDCl₃): δ 8.61 (d, 2H); 7.96 (t, 1H); 7.89 (td, 2H);7.83 (dd, 1H); 7.66 (dd, 1H); 7.52 (td, 1H); 7.49-7.43 (m, 2H); 7.40(td, 1H).

Example 2

1.63 g (10.0 mmol) of 2-chloro-1,3-dicyano-benzene, 2.07 g (10.0 mmol)of 6H-benzimidazolo[1,2-a]benzimidazole and 2.12 g (10.0 mmol) oftripotassium phosphate in 50 ml of DMF are stirred for 24 h at 150° C.The reaction mixture is cooled at room temperature and added water, thenthe precipitate is filtered off. Gradient column chromatography onsilica gel with dichloromethane/ethyl acetate (dichloromethane 100%,9/1, 4/1) gives the product. Yield 2.80 g (84%).

¹H NMR (400 MHz, CDCl₃): δ 8.19 (d, 2H); 7.95-7.87 (m, 2H); 7.86 (t,1H); 7.79 (dd, 1H); 7.49 (td, 1H); 7.46-7.35 (m, 3H); 7.15 (dt, 1H).

Example 3

1.46 g (10.0 mmol) of 1,2-dicyano-3-fluoro-benzene, 2.07 g (10.0 mmol)of 6H-benzimidazolo[1,2-a]benzimidazole and 2.12 g (10.0 mmol) oftripotassium phosphate in 50 ml of DMF are stirred for 24 h at 120° C.The reaction mixture is cooled at room temperature and added water, thenthe precipitate is filtered off. Gradient column chromatography onsilica gel with dichloromethane/ethyl acetate (dichloromethane 100%,9/1, 4/1) gives the product. Yield 3.10 g (93%).

¹H NMR (400 MHz, CDCl₃): δ 8.20 (dd, 1H); 8.05-7.96 (m, 2H); 7.90 (dd,2H); 7.79 (dd, 1H); 7.49 (td, 1H); 7.46-7.36 (m, 3H); 7.32-7.26 (m, 1H).

Example 4

0.98 g (6.71 mmol) of 1,3-dicyano-5-fluoro-benzene, 2.50 g (6.71 mmol)of 6-(3-carbazolyl)-benzimidazolo[1,2-a]benzimidazole and 1.42 g (6.71mmol) of tripotassium phosphate in 20 ml of DMF are stirred for 24 h at120° C. The reaction mixture is cooled at room temperature and addedwater, then the precipitate is filtered off. Gradient columnchromatography on silica gel with dichloromethane/ethyl acetate(dichloromethane 100%, 9/1, 4/1) gives the product. Yield 2.94 g (88%).

¹H NMR (400 MHz, CDCl₃): δ 8.56 (dd, 1H); 8.24 (d, 2H); 8.23-8.19 (m,1H); 8.07 (t, 1H); 7.94-7.89 (m, 3H); 7.81 (dt, 1H); 7.62 (dd, 1H);7.60-7.53 (m, 2H); 7.48-7.32 (m, 6H).

Example 5

5.00 g (36.0 mmol) 2,3-difluorobenzonitrile, 14.9 g (72.0 mmol)6H-benzimidazolo[1,2-a]benzimidazole and 30.5 (144 mmol) potassiumphosphate tribasic in 120 ml NMP (N-Methyl-2-pyrrolidon) are stirred at185° C. under nitrogen for 6 h.

The reaction mixture is filtered hot and the organic phase is poured onwater. The product is filtered of. Column chromatography on silica gelwith chloroform gives 6.25 g 33.9% of the product.

¹H NMR (300 MHz, DMSO-D6): rotamers: δ 8.43-8.57 (m, 2H), 7.58-8.20 (m,6H), 6.86-7.42 (m, 9H), 6.63-7.78 (m, 1H), 6.48-6.54 (m, 1H).

Example 6

5.00 g (36.0 mmol) 2,6-difluorobenzonitrile, 14.9 g (72.0 mmol)6H-benzimidazolo[1,2-a]benzimidazole and 30.5 g (144 mmol) potassiumphosphate tribasic in 150 ml NMP (N-Methyl-2-pyrrolidon) are stirred at170° C. under nitrogen for 6 h. The reaction mixture is filtered hot andthe precipitated product was filtered of. The product is decocted inDMSO. Yield 3 g 16.3% of the product.

¹H NMR (400 MHz, TFA-d1): δ 8.48-8.78 (m, 3H), 8.24-8.32 (m, 4H),7.67-7.93 (m, 12H).

Example 7

A.) 10.6 g (41.6 mmol) 2-bromo-6-fluoro-benzonitrile, 8.63 g (41.6 mmol)6H-benzimidazolo[1,2-a]benzimidazole and 30.9 (146 mmol) potassiumphosphate tribasic in 70 ml NMP (N-Methyl-2-pyrrolidon) are stirred at115° C. under nitrogen for 2 h. The reaction mixture is filtered hot andthe or organic phase is poured on water. The product is filtered of.Yield 17 g (94%).

¹H NMR (300 MHz, DMSO-D6): δ 8.22-8.34 (m, 3H), 8.02-8.05 (m, 1H),7.69-7.79 (m, 1H), 7.60-7.65 (m, 1H), 7.30-7.50 (m, 5H)

B.) 6.52 g (15.0 mmol)2-(benzimidazolo[1,2-a]benzimidazol-5-yl)-6-iodo-benzonitrile, 2.51 g(15.0 mmol) carbazole, 12.8 g (60.0 mmol) potassium phosphate tribasic,0.430 g (2.00 mmol) cupper(I) iodide and 4.00 g (35.0 mmol) DACH((±)-trans-1,2-diaminocyclohexane) in 75 ml mml dioxane are stirred at95° C. under nitrogen for 24 h.

The reaction mixture is filtered hot and the solids are washed withdioxane. The solvent is removed in vacuum. Column chromatography onsilica gel with chloroform gives 1.53 g 22% of the product.

¹H NMR (300 MHz, DMSO-D6): δ 8.25-8.34 (m, 6H), 8.08-8.11 (m, 1H),7.31-7.70 (m, 12H) MS (ESI(pos), m/z): 474 (M⁺¹).

Example 8

A.) 15.0 g 3-bromo-2-fluoro-benzonitrile (75.0 mmol), 12.9 g (77.0 mmol)carbazole, 47.8 g (225 mmol) potassium phosphate tribasic, 1.43 g (7.00mmol) cupper(I) iodide and 1.71 g (15.0 mmol) DACH((±)-trans-1,2-diaminocyclohexane) in 150 ml xylene are stirred at 115°C. under nitrogen for 20 h.

The reaction mixture is filtered hot and the solids are washed withXylene. The solvent is removed in vacuum. Column chromatography onsilica gel with chloroform/heptane 1 to 1 gives 5.7 g 27% of theproduct.

¹H NMR (300 MHz, DMSO-D6): δ 8.29 (s, 1H), 8.27 (s, 1H), 8.13-8.20 (m,1H), 7.67-7.73 (m, 1H), 7.44-7.50 (m 2H), 7.29-7.37 (m 4H)

B.) 3.50 g (12.2 mmol) 3-carbazol-9-yl-2-fluoro-benzonitrile, 2.58 g(12.5 mmol) 6H-benzimidazolo[1,2-a]benzimidazole and 10.3 g (50 mmol)potassium phosphate tribasic in 35 ml NMP (N-Methyl-2-pyrrolidon) arestirred at 170° C. under nitrogen for 18 h.

The reaction mixture is filtered hot and the precipitated product wasfiltered of. Column chromatography on silica gel with dichloromethanegives 1.70 g 29% of the product.

¹H NMR (300 MHz, DMSO-D6): δ 8.46 (dd, 1H), 8.29 (dd. 1H), 8.13 (t, 1H),7.96-8.00 (m, 2H), 7.85 (d, 1H), 7.80 (d, 1H), 7.67 (d, 1H), 7.58 (d,1H), 7.41-7.46 (m, 1H), 7.31-7.37 (m, 1H) 7.22-7.27 (m, 2H), 7.00-7.707(m, 2H), 6.87-6.93 (m, 2H), 6.66-6.73 (m, 2H).

MS (ESI(pos), m/z): 474 (M⁺¹).

Example 9

A.) 10.6 g (41.6 mmol) 2-fluoro-6-iodo-benzonitrile, 8.63 g (41.6 mmol)6H-benzimidazolo[1,2-a]benzimidazole and 30.9 (146 mmol) potassiumphosphate tribasic in 70 ml NMP (N-Methyl-2-pyrrolidon) are stirred at115° C. under nitrogen for 2 h.

The reaction mixture is filtered hot and the organic phase is poured onwater. The product is filtered of. Yield 17 g (94%)

¹H NMR (300 MHz, DMSO-D6): δ 8.22-8.34 (m, 3H), 8.02-8.05 (m, 1H),7.69-7.79 (m, 1H), 7.60-7.65 (m, 1H), 7.30-7.50 (m, 5H)

B.) 4.20 g (9.67 mmol)2-(benzimidazolo[1,2-a]benzimidazol-5-yl)-6-iodo-benzonitrile, 4.44 g(9.67 mmol)9-[8-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)dibenzofuran-2-yl]carbazole,8.21 g (39.0 mmol) potassium phosphate tribasic in 30 ml dioxane, 60 mltoluene and 24 ml water are degased with argon. 0.2 g (0.9 mmol)palladium(II)acetate is added and the reaction mixture is degased withargon. 0.93 g (2.2 mmol) SPhos(2-Dicyclohexylphosphino-2′,6′-dimethoxybiphenyl) is added and thereaction mixture is degased with argon. The reaction mixture is refluxedunder argon for 18 h.

The organic layer is washed with a 1% solution of NaCN in water and thenthe organic phase is washed with water. The organic phase is dried withMagnesium sulfate and the solvent is removed in vacuum.

Column chromatography on silica gel with dichloromethane gives 1.450 g23% of the product.

¹H NMR (300 MHz, DMSO-D6): δ 8.58-8.71 (m, 2H), 7.78-8.31 (m, 11H),7.59-7.65 (m, 1H), 7.25-7.50 (m, 11H)

MS (APCI(pos), m/z): 640 (M⁺¹).

Example 10

A.) 15.0 g (75.0 mmol) 3-bromo-2-fluoro-benzonitrile, 15.5 g (75 mmol)6H-benzimidazolo[1,2-a]benzimidazole and 47.8 (225 mmol) potassiumphosphate tribasic in 100 ml NMP (N-Methyl-2-pyrrolidon) are stirred at105° C. under nitrogen for 3.5 h.

The reaction mixture is filtered hot and the organic phase is poured onwater. The product is filtered of. Yield 26.4 g (91%)

¹H NMR (300 MHz, DMSO-D6): δ 8.37-8.41 (m, 1H), 8.27-8.32 (m, 3H),7.83-7.88 (t, 1H, J=2*8 Hz), 7.60-7.66 (m, 1H), 7.25-7.53 (m, 5H)

B.) 5.00 g (12.9 mmol)2-(benzimidazolo[1,2-a]benzimidazol-5-yl)-3-bromo-benzonitrile, 5.93 g(12.9 mmol)9-[8-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)dibenzofuran-2-yl]carbazole,11.0 g (52.0 mmol) potassium phosphate tribasic in 32 ml dioxane, 80 mltoluene and 24 ml water are degased with argon. 0.1 g (0.5 mmol)palladium(II)acetate is added and the reaction mixture is degased withargon. 0.46 g (1 mmol) SPhos(2-Dicyclohexylphosphino-2′,6′-dimethoxybiphenyl) is added and thereaction mixture is degased with argon. The reaction mixture is refluxedunder argon for 18 h.

The organic layer is washed with a 1% solution of NaCN in water and thenthe organic phase is washed with water. The organic phase is dried withMagnesium sulfate and the solvent is removed in vacuum.

Column chromatography on silica gel with dichloromethane gives 3 g 36%of the product.

¹H NMR (300 MHz, DMSO-D6): δ 7.98-8.32 (m, 9H), 7.87-7.90 (d, 1H),7.67-7.70 (dd, 1H), 7.03-7.55 (m, 14H),

Example 11

5.00 g (31.8 mmol) 3-bromo-2-fluoro-benzonitrile, 23.1 g (111 mmol)6H-benzimidazolo[1,2-a]benzimidazole and 60.8 (0.286 mol) potassiumphosphate tribasic in 120 ml NMP (N-Methyl-2-pyrrolidon) are stirred at30° C. under nitrogen for 30 min. Then the reaction mixture is stirredat 120° C. for 4 h.

The reaction mixture is filtered hot and is washing with water. Theproduct is crystalized from DMSO. The product is filtered of. Yield 2.5g (11%)

¹H NMR (300 MHz, DMSO-D6): δ 6.44-8.33 (m, 26H)

Example 12

2.5 g (15.9 mmol) 2,3,4-trifluorobenzonitrile, 10.9 g (52.5 mmol)6H-benzimidazolo[1,2-a]benzimidazole and 27.0 g (0.127 mol) potassiumphosphate tribasic in 50 ml NMP (N-Methyl-2-pyrrolidon) are stirred at115° C. under nitrogen for 18 h. The reaction mixture is filtered hotand the organic phase is poured on water. The product is filtered of.Column chromatography on silica gel with chloroform gives 1.3 g (11.4%)of the product

¹H NMR (300 MHz, DMSO-D6): rotamers: δ 8.55-8.82 (m, 2H); 6.41-8.07 (m,24H)

MS (APCI(pos), m/z): 719 (M⁺¹).

Example 13

4.0 g (28.8 mmol) 3,5-difluorobenzonitrile, 11.9 g (57.6 mmol)6H-benzimidazolo[1,2-a]benzimidazole and 36.6 g (173 mmol) potassiumphosphate tribasic in 50 ml NMP (N-Methyl-2-pyrrolidon) are stirred at180° C. under nitrogen for 7 h. The reaction mixture is filtered hot.Washing with water. Yield 6.6 g 47.7% product

¹H NMR (400 MHz, TFA-d1): δ 8.87 (m, 1H); 8.70 (s, 1H); 8.69 (s, 1H);8.28 (d, J=8.1 Hz 2H) 8.21-8.23 (m, 2H); 7.75-7.90 (m, 8H)

Example 14

1.50 g (10.7 mmol) 2,6-difluorobenzonitrile, 8.19 g (22.0 mmol)5-(9H-carbazol-3-yl)-5H-benzo[d]benzo[4,5]imidazo[1,2a]imidazole and10.7 g (47.5 mmol) potassium phosphate tribasic in 30 ml NMP(N-Methyl-2-pyrrolidon) are stirred at 130° C. under nitrogen for 7 h.The reaction mixture is filtered hot and the organic phase is poured onwater. The product is filtered of. Column chromatography on silica gelwith chloroform gives 4.7 g (51.6%) of the product.

¹H NMR (400 MHz, DMSO-D6): δ 8.80-8.81 (d, 2H), 8.38-8.45 (m, 3H),8.21-8.32 (m, 6H), 8.01-8.03-7.50 (t, 1H), 7.99-8.00 (t, 1H), 7.82-7.83(d, 1H), 7.80-7.81 (d, 1H), 7.59-7.65 (m, 8H), 7.27-7.48 (m, 10H)

Example 15

222 mg NaH (60% in mineral oil) and 304 mg (1.85 mmol)4,5-difluorophtalonitril is added to a solution of 960 mg (4.63 mmol)benzimidazolo[1,2-a]benzimidazole in 275 ml N,N-dimethylformamide andstirred 1.5 hours at room temperature. The reaction is quenched with 550ml distilled water, the precipate is filtered, washed three times withdistilled water, and dried under vacuum at 60° C. The product ispurified under chromatography using a 19:1 CH₂Cl₂/THF mixture andobtained as a fine bright yellow powder (99.6% purity, 886 mg, 89%yield). 1H-NMR (DMSO; 500 MHz): δ (ppm) 9.05 (d, 2H); 7.99 (d, 1H); 7.9(m, 2H); 7.80 (d, 1H); 7.51 (d, 1H); 7.23 (m, 7H); 7.00 (m, 3H); 6.785(t, 1H).

Example 16

9-fluorodibenzofuran-2-carbonitrile (1.6 g, 7.58 mmol),6H-benzimidazolo[1,2-a]benzimidazole (1.65 g, 7.96 mmol), and potassiumphosphate (3.38 g, 15.91 mmol) are suspended in 39 mL of NMP, and themixture is stirred at 185° C. for 14 h. After the reaction mixture iscooled at room temperature, it is diluted with 76 mL of water and 38 mLof EtOH. The solid is collected by filtration, and dried in vacuum ovenat 50° C. The crude product is purified by column chromatography onsilica gel eluting with chloroform to yield 2.21 g (73%) of9-(benzimidazolo[1,2-a]benzimidazol-5-yl)dibenzofuran-2-carbonitrile asa white solid.

¹H-NMR (300 MHz, DMSO-d₆): δ 8.36-8.26 (m, 2H), 8.08-7.83 (m, 5H),7.61-7.54 (m, 2H), 7.48 (td, J=1.1, 7.8 Hz, 4H), 7.36-7.30 (m, 3H), 7.19(d, J=7.8 Hz, 1H)

Example 17

A.) 10 g (50.0 mmol) 3-bromo-4-fluoro-benzonitrile, 9.33 g (45 mmol)6H-benzimidazolo[1,2-a]benzimidazole and 31.8 g (150 mmol) K₃PO₄ areadded to 100 ml DMF and the suspension is heated to 110° C. for 23 h.The reaction mixture is filtered hot through Hyflo and the filtrate isevaporated on the rotavap to yield 18.6 g of crude product. The crudeproduct is suspended in 100 ml MeOH, stirred at RT for 2 h, filtered anddried at 80° C./125 mbar overnight to yield 15.1 g of a beige product.Recrystallization from 500 ml EtOAc yields

13.5 g (69.7% of theory)2-(benzimidazolo[1,2-a]benzimidazol-5-yl)-3-bromo-benzonitrile as whitesolid.

¹H-NMR (400 MHz, CDCl₃): δ 8.08 (d×d, J₁=8.4 Hz, J₂=1.6 Hz, 1H),7.90-7.865 (m, 3H), 7.76 (d, J=7.6 Hz, 1H), 7.57 (t, J=8.0 Hz, 1H),7.44-7.30 (m, 4H), 7.01 (d, J=8.0 Hz, 1H)

B.) 40 g (160.3 mmol) 2-bromo-dibenzofuran are dissolved in 250 ml THFabs. and cooled to −78° C. 65 ml (175.5 mmol) BuLi (2.7M in hexane) areadded within 55 min while keeping the internal temperature below −73° C.The resulting suspension is stirred for 30 min followed by the additionof 33.5 g (176.3 mmol)2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane within 30 min whilekeeping the internal temperature below −73° C. The reaction mixture isthen slowly brought to RT, then 200 ml of buffer solution pH=7 are addedand the pH brought to 7 by the addition of HCl 4M. The organic solventis then evaporated on the rotavap; the aqueous phase is extracted threetimes with EtOAc (250 ml each). The combined organic phases are washedthree times with H₂O (200 ml each), dried over Na₂SO₄, filtered andevaporated. The crude product (51.7 g) is purified by CombiFlashchromatography (solvent: Heptane/CH₂Cl₂ (0 to 40%)) to yield 34.1 g of acolorless oil. 100 ml MeOH are added, the mixture is heated to reflux,cooled to RT and then to 0° C. The suspension is filtered and theresidue is dried at 30° C./125 mbar overnight to yield 28.3 g (60.0% oftheory) 2-dibenzofuran-2-yl-4,4,5,5-tetramethyl-1,3,2-dioxaborolane as awhite solid.

¹H-NMR (300 MHz, CDCl₃): 8.45 (s (1H), 7.99-7.92 (m. 2H), 7.59-7.55 (m,2H), 7.48 (t, J=7.2 Hz, 1H), 7.37 (t, J=7.8 Hz, 1H), 1.40 (s, 12H).

C.) 7.68 g (19.8 mmol)2-(benzimidazolo[1,2-a]benzimidazol-5-yl)-3-bromo-benzonitrile and 7.0 g(23.8 mmol) 2-dibenzofuran-2-yl-4,4,5,5-tetramethyl-1,3,2-dioxaborolaneare dissolved in 140 ml THF and the solution is evacuated and purgedthree times with argon. 0.35 g (1.2 mmol) P(t-Bu)₃.HBF₄ and 0.54 g (0.6mmol) Pd₂(dba)₃ are added and the solution is evacuated and purged threetimes with argon and heated to 50° C. A solution of 12.6 g (59.5 mmol)K₃PO₄ in 35 ml H₂O (evacuated and purged three times with argon) isadded with a syringe and the reaction mixture is heated to reflux for 17h. To the cooled reaction mixture are added 300 ml EtOAc and the phasesare separated. The organic phase is washed three times with brine (100ml each), dried over MgSO₄ filtered and evaporated on the rotavap toyield 13.3 g of crude product. Flash chromatography usingCH₂Cl₂/EtOAc=9:1 as eluent

yields 7.23 g (68.0% of theory)2-(benzimidazolo[1,2-a]benzimidazol-5-yl)-3-dibenzofuran-2-yl-benzonitrileas a white solid.

¹H-NMR (300 MHz, CDCl₃): δ 7.97 (m, 2H), 7.84-7.71 (m, 4H), 7.64 (d,J=7.6 Hz, 1H), 7.53 (d, J=8.0 Hz, 1H), 7.44 (d, J=8.0 Hz, 1H), 7.39-7.33(m, 2H), 7.28-7.11 (m, 6H), 6.90 (d, J=7.6 Hz, 1H).

Example 18

A.) 20.0 g (87.3 mmol) 3-bromo-benzonitrile, 16.6 g (80.0 mmol)6H-benzimidazolo[1,2-a]benzimidazole, 67.9 g (320 mmol) potassiumphosphate tribasic, 1.5 g (7.88 mmol) cupper(I) iodide and 100 g (875mmol) DACH ((±)-trans-1,2-diaminocyclohexane) in 240 ml dioxane arestirred at 100° C. under nitrogen for 7 h.

The reaction mixture is filtered hot and the solids are washed withdioxane. The reaction mixture is cooled to 50° C. and the crystalizedproduct is filtered of and is washed with methanol. Yield 11.2 g (46%)

¹H-NMR (300 MHz, CDCl₃): δ 7.33-7.49 (m, 4H), 7.59-7.63 (d, 1H),7.72-7.83 (m, 3H), 7.86-7.90 (d, 2H), 8.22-8.26 (m, 2H),

B.) 11.2 g (36.3 mmol)3-(benzimidazolo[1,2-a]benzimidazol-5-yl)benzonitrile, 11.7 g (36.3mmol) diacetoxy-iodobenzene, 9.22 g (36.3 mmol) iodine in 90 ml aceticacid are stirred under nitrogen at 25° C. for 18 h. The product isfiltered off and is washed with methanol and methanol water 95 to 5.Yield: 12.8 g (81%)

¹H-NMR (300 MHz, CDCl₃): δ 7.39-7.61 (m, 4H), 7.66-7.70 (d, 1H),7.73-7.86 (m, 3H), 8.18-8.23 (m, 3H)

C.) To 10.0 g (20.7 mmol)3-(2-iodobenzimidazolo[1,2-a]benzimidazol-5-yl)benzonitrile, 8.18 g(31.1 mmol) triphenylsilane, 17.6 g (82.9 mmol) potassium phosphate in125 ml dimethylformamide is degassed with argon. 500 mg (1.131 mmol)Rhodium(II)-acetate is added and the reaction mixture is degassed withargon. The reaction mixture is stirred at 60° C. for 18 h under argon.250 mg 500 mg (0.566 mmol) Rhodium(II)-acetate is added and the reactionmixture is stirred for 18 h under argon. The reaction is filtered andthe filtrate is caped for crystallization. Column chromatography withchloroform gives the product. Yield 1.5 g (12.8%)

¹H-NMR (300 MHz, CDCl₃): δ 7.36-7.86 (m, 23H), 8.02 (s, 1H), 8.20-8.26(m, 2H)

Example 19 (Comparative)

3.00 g (6.91 mmol) of3-(2-iodobenzimidazolo[1,2-a]benzimidazol-5-yl)benzonitrile (see example18), 1.39 g (8.29 mmol) carbazol, 4.40 g (20.7 mmol) potassium carbonatetribasic, 260 mg (1.38 mmol) copper iodide in 70 ml dioxane are stirredat 100° C. under nitrogen. 5.52 g (48.4 mmol) 1,2-diaminocyclohexne isadded and the reaction mixture is stirred at 100° C. under nitrogen for25 h.

The reaction mixture is poured on methanol and the product is filteredof. The product is washed with water and methanol. Column chromatographyon silica gel with dichloromethane and 0.2% methanol give the product.

¹H-NMR (CDCl₃): d 8.29-8.26 (m, 2H), 8.24-8.21 (m, 2H), 8.04 (d, 1H),7.99 (d, 1H), 7.85-7.77 (m, 3H), 7.65-7.58 (m, 2H), 7.48-7.40 (m, 6H),7.37-7.32 (m, 2H).

II Application Examples Comparative Application Example 1

A glass substrate with 120 nm-thick indium-tin-oxide (ITO) transparentelectrode used as an anode is first cleaned with isopropanol in anultrasonic bath for 10 min. To eliminate any possible organic residues,the substrate is exposed to an ultraviolet light and ozone for further30 min. This treatment also improves the hole injection properties ofthe ITO. The cleaned substrate is mounted on a substrate holder andloaded into a vacuum chamber. Thereafter, the organic materialsspecified below are applied by vapor deposition to the ITO substrate ata rate of approx. 0.2-1 Å/sec at about 10⁻⁶-10⁻⁸ mbar. As a holeinjection layer, compound

with 30 nm thickness is applied. Then compound

with 60 nm thickness is applied as a hole transporting layer. As anexciton and electron blocker, compound

(HTM-1; for preparation, see Ir complex (7) in the applicationWO2005/019373) is then applied with a thickness of 10 nm. Subsequently,a mixture of 20% by weight of emitter compound,

15% by weight of compound (HTM-1) and 65% by weight of host

are applied to form a 40 nm-thick emitting layer. On the emitting layer,5 nm-thick material (SH-1) is applied as an exciton blocker. Thereafter,compound

with 20 nm thickness is deposited as an electron transport layer.Finally, 1 nm-thick LiF is deposited as an electron injection layer and80 nm-thick Al is then deposited as a cathode to complete the device.The device is sealed with a glass lid and a getter in an inert nitrogenatmosphere with less than 1 ppm of water and oxygen.

OLED Characterization

To characterize the OLED, electroluminescence spectra are recorded atvarious currents and voltages. In addition, the current-voltagecharacteristic is measured in combination with the luminance todetermine luminous efficiency and external quantum efficiency (EQE).Driving voltage U and EQE are given at luminance (L)=1000 cd/m² exceptotherwise stated.

Application Example 1 (Inventive)

Comparative Application Example 1 is repeated except that the host(SH-1) is replaced by compound

preparation Example 13). The device results are shown in Table 1.

Application Example 2 (Inventive)

Comparative Application Example 1 is repeated except that the host(SH-1) is replaced by compound

preparation Example 5). The device results are shown in Table 1.

Application Example 3 (Inventive)

Comparative Application Example 1 is repeated except that both the host(SH-1) and exciton blocker (SH-1) are replaced by compound

preparation Example 5). The device results are shown in Table 1.

TABLE 1 Luminous Exciton efficiency Appl. Ex. Host blocker U [V] [lm/W]Comp. Appl. Ex. 1 (SH-1) (SH-1) 5.46 17.7 Appl. Ex. 1 (13)  (SH-1) 4.8319.3 Appl. Ex. 2 (5) (SH-1) 4.55 22.7 Appl. Ex. 3 (5) (5) 4.18 23.0

The results shown in Table 1 demonstrate that the driving voltage U issignificantly reduced with increasing luminous efficiency at the sametime when compounds (5) or (13) is used as the host instead of referencecompound (SH-1). Furthermore, when compound (5) is used as both the hostand exciton blocker, the driving voltage U is further reduced and theluminous efficiency is also improved.

Comparative Application Example 2

A glass substrate with 120 nm-thick ITO is cleaned and treated in thesame manner as comparative application example 1. As a hole injectionlayer, compound

with 30 nm thickness is applied by vapor deposition. Then 60 nm ofcompound (SH-1) doped with MoOx (˜10%) is deposited as hole transportinglayer. MoOx is used to improve the hole conductivity of SH-1. As anexciton and electron blocker, compound (SH-1) is applied with athickness of 10 nm. Subsequently, a mixture of 20% by weight of emittercompound (BE-1) and 80% by weight of host (SH-1) are applied to form a40 nm of emitting layer. On the emitting layer, 5 nm of material (SH-1)is applied as an exciton blocker. Thereafter, compound

with 20 nm thickness is deposited as an electron transport layer.Finally, 1 nm of LiF is deposited as an electron injection layer and 80nm of Al is then deposited as a cathode to complete the device. Thedevice is sealed with a glass lid and a getter in an inert nitrogenatmosphere with less than 1 ppm of water and oxygen.

Application Example 4 (Inventive)

Comparative Application Example 2 is repeated except that both the host(SH-1) and exciton blocker (SH-1) is replaced by compound

preparation Example 6). The device results are shown in Table 2.

Application Example 5 (Inventive)

Comparative Application Example 2 is repeated except that both the host(SH-1) and exciton blocker (SH-1) is replaced by compound

preparation Example 5). The device results are shown in Table 2.

TABLE 2 Luminous Exciton efficiency Appl. Ex. Host blocker U [V] [lm/W]Comp. Appl. Ex. 2 (SH-1) (SH-1) 5.54 1.2 Appl. Ex. 4 (6) (6) 4.52 23.3Appl. Ex. 5 (5) (5) 3.87 27.1

The results shown in Table 2 demonstrate that the driving voltage andthe luminous efficiency are improved when compounds (5) or (6) are usedas host and exciton blocker instead of reference compound (SH-1).

1: A compound of formula (I):

wherein: X³ is a single bond or linking group of formula-(A¹)_(o′)-(A²)_(p′)-(A³)_(q′)-(A⁴)_(r′)-, A¹, A², A³, A⁴ are in eachoccurrence independently of each other C₆-C₂₄ arylene group which isunsubstituted or substituted by at least one group G, C₂-C₃₀heteroarylene group which is unsubstituted or substituted by at leastone group G, o′ is 0 or 1, p′ is 0 or 1, q′ is 0 or 1, r′ is 0 or 1, X⁴is a single bond or

X² is O, S or NR⁶⁵; X⁵ is O, S or NR⁶⁵; a is 0, 1, 2, 3 or 4, b is 0, 1,2, 3 or 4, a′ and a″ are independently of each other 0, 1, 2 or 3, b′and b″ are independently of each other 0, 1, 2 or 3, X¹, X^(1′) andX^(1″) are independently of each other a group of formula-(A¹)_(o)-(A²)_(p)-(A³)_(q)-(A⁴)_(r)-R₁₀, in each occurrence o is 0 or1, p is 0 or 1, q is 0 or 1, r is 0 or 1; R¹⁰ is H,

R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R^(a) and R^(b) are in eachoccurrence independently H, C₆-C₂₄ aryl group which is unsubstituted orsubstituted by at least one group G, C₂-C₃₀ heteroaryl group which isunsubstituted or substituted by at least one group G, a C₁-C₂₅alkylgroup, which is unsubstituted or substituted by at least one group Eand/or interrupted by D, C₆-C₂₄ aryloxy group which is unsubstituted orsubstituted by at least one group G, or —SiR⁷⁰R⁷¹R⁷²; or two groups R¹and R² or R² and R³ or R³ and R⁴ of formulae IV can form together thefollowing ring system:

wherein t is 1 to 5; D is —CO—, —COO—, —S—, —SO—, —SO₂—, —O—,—CR⁶³═CR⁶⁴—, —NR⁶⁵—, —SiR⁷⁰R⁷¹—, —POR⁷²—, or —C≡C—, E is —OR⁶⁹, —SR⁶⁹,—NR⁶⁵R⁶⁶, —COR⁶⁸, —COOR⁶⁷, —CONR⁶⁵R⁶⁶, —CN, —SiR⁷⁰R⁷¹R⁷², halogen, anunsubstituted C₆-C₂₄aryl group, a C₆-C₂₄aryl group, which is substitutedby F, C₁-C₁₈alkyl, C₁-C₁₈alkyl which is interrupted by O, anunsubstituted C₂-C₃₀heteroaryl group, or a C₂-C₃₀heteroaryl group, whichis substituted by F, C₁-C₁₈alkyl, C₁-C₁₈alkyl which is interrupted by O;G is E, or a C₁-C₁₈alkyl group, or C₁-C₁₈alkyl which is interrupted byO, R⁶³ and R⁶⁴ are independently of each other C₆-C₁₈aryl; C₆-C₁₈arylwhich is substituted by C₁-C₁₈alkyl, C₁-C₁₈alkoxy; C₁-C₁₈alkyl; orC₁-C₁₈alkyl which is interrupted by —O—; R⁶⁵ and R⁶⁶ are independentlyof each other a C₆-C₁₈aryl group; a C₆-C₁₈aryl which is substituted byC₁-C₁₈alkyl, or C₁-C₁₈alkoxy; a C₁-C₁₈alkyl group; or a C₁-C₁₈alkylgroup, which is interrupted by —O—; or R⁶⁵ and R⁶⁶ together form a fiveor six membered ring, R⁶⁷ is a C₆-C₁₈aryl group; a C₆-C₁₈aryl group,which is substituted by C₁-C₁₈alkyl, or C₁-C₁₈alkoxy; a C₁-C₁₈alkylgroup; or a C₁-C₁₈alkyl group, which is interrupted by —O—, R⁶⁸ is H; aC₆-C₁₈aryl group; a C₆-C₁₈aryl group, which is substituted byC₁-C₁₈alkyl, or C₁-C₁₈alkoxy; a C₁-C₁₈alkyl group; or a C₁-C₁₈alkylgroup, which is interrupted by —O—, R⁶⁹ is a C₆-C₁₈aryl; a C₆-C₁₈aryl,which is substituted by C₁-C₁₈alkyl, or C₁-C₁₈alkoxy; a C₁-C₁₈alkylgroup; or a C₁-C₁₈alkyl group, which is interrupted by —O—, R⁷⁰ and R⁷¹are independently of each other a C₁-C₁₈alkyl group, a C₆-C₁₈aryl group,or a C₆-C₁₈aryl group, which is substituted by C₁-C₁₈alkyl, and R⁷² is aC₁-C₁₈alkyl group, a C₆-C₁₈aryl group, or a C₆-C₁₈aryl group, which issubstituted by C₁-C₁₈alkyl, wherein the following compound is excluded:

2: A compound as claimed in claim 1, wherein: a is 0, 1, 2 or 3, b is 0,1, 2 or 3, the sum of a+b is 1, 2 or 3, a′ and a″ are independently ofeach other 0, 1, 2 or 3, and b′ and b″ are independently of each other0, 1, 2 or
 3. 3: A compound as claimed in claim 1, wherein in eachoccurrence o is 0 or 1, p is 0 or 1, and q and r are
 0. 4: A compound asclaimed in claim 1, wherein: X⁴ is a single bond or

5: A compound as claimed in claim 1, wherein the compound has theformula (Ia):

wherein: R³, R⁷ are independently of each other H or a group of thefollowing formula:

or —SiR⁷⁰R⁷¹R⁷², R⁷⁰ and R⁷¹ are independently of each other aC₁-C₁₈alkyl group, a C₆-C₁₈aryl group, or a C₆-C₁₈aryl group, which issubstituted by C₁-C₁₈alkyl, and R⁷² is a C₁-C₁₈alkyl group, a C₆-C₁₈arylgroup, or a C₆-C₁₈aryl group, which is substituted by C₁-C₁₈alkyl. 6: Acompound as claimed in claim 1, wherein: A¹, A², A³, A⁴ are in eachoccurrence independently of each other a group of the formula:

(C)— has the meaning that the bonding site of the group A¹, A², A³ or A⁴is linked to a C-atom, and (N)— has the meaning that the bonding site ofthe group A¹, A², A³ or A⁴ is linked to a N-atom. 7: A compound asclaimed in claim 1, wherein: R¹⁰ is H or a group of the followingformula:

8: A compound as claimed in claim 1, wherein: X³ is a single bond or agroup of the following formula:

9: A compound as claimed in claim 1, wherein the compound has theformula (Ib):

wherein: a is 0 or 1, b is 0 or 1, the sum of a and b is at least 1; X¹is a group of the following formula:

X³ is a single bond or a group of the following formula:

R⁷ is H or group of the following formula:

or —SiR⁷⁰R⁷¹R⁷², R⁷⁰ and R⁷¹ are independently of each other aC₁-C₁₈alkyl group, a C₆-C₁₈aryl group, or a C₆-C₁₈aryl group, which issubstituted by C₁-C₁₈alkyl, and R⁷² is a C₁-C₁₈alkyl group, a C₆-C₁₈arylgroup, or a C₆-C₁₈aryl group, which is substituted by C₁-C₁₈alkyl. 10:An electronic device, comprising a compound according to claim
 1. 11:The electronic device according to claim 10, which is anelectroluminescent device. 12: A charge transport layer, acharge/exciton blocker layer, or an emitting layer, comprising acompound according to claim
 1. 13: The emitting layer according to claim12, comprising the compound as host material. 14: An apparatus selectedfrom the group consisting of stationary visual display units; mobilevisual display units; illumination units; keyboards; items of clothing;furniture; wallpaper, comprising the organic electronic device accordingto claim
 10. 15: An article, comprising the compound of claim 1, whereinthe article is selected from the group consisting of anelectrophotographic photoreceptor, a photoreceptors, photoelectricconverter, an organic solar cell, a switching element, an organic lightemitting field effect transistor, an image sensor, a dye laser and anelectroluminescent device. 16: The emitting layer according to claim 12,comprising at least one compound of formula I as TADF emitter or as TADFhost material in combination with at least one fluorescent emitter. 17:An apparatus selected from the group consisting of stationary visualdisplay unit, mobile visual display unit, illumination unit, keyboard,item of clothing, furniture, wallpaper, said apparatus comprising thecharge transport layer, the charge/exciton blocker layer, or theemitting layer according to claim 12.